For the bounty on British heads, Wong cites a document in the British Parliamentary Papers, which I have access to. I was not able to locate his specific reference, but the proclamation is included in translation in the collection of 'Papers Relating to the Proceedings of Her Majesty's Naval Forces at Canton', p. 40. (The original, as with most such documents in the Parliamentary collection, has probably been lost, but it was sent back to be translated.) It reads:

YEH, the Governor General, proclaims the following:

The English barbarians have attacked the provincial city, and wounded and injured our soldiers and people. Their crimes are indeed of the most heinous nature.

Wherefore I herewith distinctly command you to join together to exterminate them, and I publicly proclaim to all the military and people, householders and others, that you should unite with all the means at your command, to assist the soldiers and militia in exterminating these troublous English villains, killing them whenever you meet them, whether on shore or in their ships. For each of their lives that you may thus take you shall receive, as before, thirty dollars. All ought to respect and obey, and neither oppose nor disregard this special proclamation.

Heen-fung [Xianfeng], 6th year, 9th month, 30th day (October 28, 1856).

So that seems pretty clear. The bounty and proclamation are mentioned elsewhere a few times in the British correspondence, and was also applied to Red Turban rebels by Ye in another proclamation two days later, in which he accused them of collaborating with the British:

YEH, Governor-General of the Two Kwang Provinces, &c., issues these urgent and distinct orders to quiet the minds of the people.

The rebels of the Hung faction [the Red Turbans] have now combined with the English ships to attack the provincial city, with no other object, it certainly may be inferred, than that of spoliation and destruction. I, the Governor-General, have now however posted soldiers and militia in every direction, and have made such secret arrangements as should ensure the complete annihilation of this hateful brood, and thus appease the anger of the people. It only remains for the whole population, whether military, householders, or others, to preserve quiet minds, guard their own property, and maintain in their several streets a careful watch after traitorous spies, whom they should search out and apprehend. You should not therefore give way to alarm or think of removing (from the city), but will of course join with each other in measures of revenge. If you can indeed seize any of the Hung rebels, and can prove them to be such, a reward of thirty dollars shall be paid you at my office for every one of them so seized, whether dead or alive. And this thereby make known by proclamation to all classes oft he people for their information and guidance.

A special proclamation.

Heen-fung [Xianfeng], 6th year, 10th month, 2nd day, (30th October 1856.)

In fact, Ye seems to have raised the stakes later, according to a translation published in the China Mail on 27 November:

Whoever catches an English or French rebel chief will receive a reward of 5000 dollars. Whoever cuts off the head of a rebel barbarian will receive a reward of 50 dollars. Whoever catches a rebel barbarian alive will receive a reward of 100 dollars. Whoever catches a traitor, will, on producing satisfactory evidence, receive a reward of 20 dollars. Whoever can manage to burn or take a large war steamer will receive a reward of 10,000 dollars. Whoever can manage to burn or take a shallow water steamer will receive 200 dollars, and can be remembered for further reward.

As for the Thistle, Wong again cites the Parliamentary Papers, in this case a letter from Hong Kong Governor Sir John Bowring to Lord Clarendon, the Foreign Secretary, written on 31 December 1856:

My Lord, Hong Kong, December 31, 1856.

I AM sorry to have to report to your Lordship one of those acts of treacherous surprise which have been too often successfully practised by the Chinese, and which, indeed, cause us more anxiety and apprehension than any open hostilities.

The postal steamer "Thistle" was yesterday on her way from Canton to Hong Kong. She took in, it seems, a number of Imperialist soldiers in disguise, who rose upon the captain and crew, murdered the captain, mate, engineers, and passengers, and, as I am informed, after setting the ship on fire, departed for Canton with the heads of their victims.

I inclose copy of a letter I have just received from the agent of the steamer, which I have immediately communicated to the Naval Commander-in-chief.

I have, &c.

(Signed) JOHN BOWRING.

In this case, it is true that a British rather than a Chinese source is being cited, but it is corroborated in American correspondence and in contemporary newspapers (note: while this is the Sydney Morning Herald, the highlighted columns on China matters are quoted from the Friend of China (Hong Kong) and North China Herald (Shanghai).)

Now, the fascinating incident is the arsenic poisoning. This is perhaps better remembered in the context of the history of colonial Hong Kong rather than the Arrow War, but needless to say, the Esing Bakery Poisoning is one of those events that hit home how vulnerable the colony was in the first winter of the war, when hostilities had been declared but there was no expeditionary force in place. The Esing Bakery was set up by a compradore named Cheong Alum near the Hung Shing Temple on Queen's Road (about 1km from where I'm writing this answer), and was by 1856 one of the largest in Hong Kong, with contracts for supplying the Royal Navy and the colonial garrison. This made it a particularly attractive target for poisoners, although in the event only 500 or so people, mostly civilians, suffered symptoms, as the garrison ate its breakfast with bread from the day before.

Cheong, who had left Hong Kong shortly after the bakery opened in order to get his family to safety in Canton, was intercepted and arrested, and eventually 52 suspects were jailed awaiting trial. Governor Bowring insisted on a jury trial rather than a summary court martial, which proved fortunate for Cheong, as he was able to prove that he had no intention of poisoning people and fleeing, given that he had made a large order of flour for the next day. On 6 February, the jury voted 5-1 that Cheong and the other 9 primary suspects were 'not guilty'. But Cheong was arrested again immediately after for being a 'suspicious character', and jailed until 31 July, when he was exiled.

The actual poisoners were never found, as there was never any physical evidence linking anyone to the act. The trial in fact largely took the form of an examination of Cheong's character, with the defence arguing that Cheong was a well-respected businessman with a spotless record, the prosecution that this was a front for his real status as a Qing sleeper agent. Lowe and McLaughlin, whose 2015 article on the poisoning is the most recent and most detailed, suggest three possible explanations for the poisoning:

1. Cheong or one of his employees actually was a Qing sleeper agent, acting on orders from Ye Mingchen or someone else in the Qing government;
2. Cheong's bakery was targeted by one of his business rivals, who was trying to shut down the bakery; or
3. The poisoning was an accident, the white arsenic having been confused for flour.

There is circumstantial evidence to support all of these. If there was indeed a sleeper agent, then targeting the bakery made sense, as the consumers of European-style bread would primarily have been the colony's white population. Moreover, Cheong's bakery was especially productive and had particularly high-profile customers, allegedly supplying up to 400 families on top of quite substantial contracts with the government, the navy, the army and several shipping firms. But there were also at least 6 other major competing bakeries active in Hong Kong (plus at least 14 smaller ones), and those potentially lucrative contracts would be up for grabs if Cheong were put out of business. Yet the quantity of arsenic was probably too much to be fatal, as the amount present in even a single slice of toast (as subsequently analysed by a chemist at the War Department in London) would induce vomiting and so prevent much poison from being ingested. It might be reasonable to infer that either the poisoning was attempted by a complete amateur, or that it was an unintentional introduction of powdered arsenic in place of flour, which has similar physical properties. Given how relatively common white arsenic would have been for medicinal purposes in Hong Kong, and how relatively uncommon wheat flour for breadmaking would have been, this is not an unreasonable suggestion. In the long run, only three deaths would be connected with long-term effects of the poisoning: two in January 1858, and one, the governor's wife Lady Maria Bowring, in September 1857. Lady Bowring, it was noted, was perhaps at most risk as she ate the least bread, and so vomited very little of it back up.