How much truth is there to the statement that Erwin Rommel and his Afrikacorps were humane and did not commit war crimes? How likely was it that he would be punished at the Nuremburg Trials, had he not been forced to commit suicide?

I would hesitate to describe Rommel as 'humane'... in fact, no, he was not humane - that would imply he was compassionate and kind. He was not - this guy was a hard-boiled blood-soaked muddy-boots warrior of a rare sort, make no mistake about it.

That said, neither was he particularly cruel. He was not prone to the barbarous lunacy of say, Reichenau (commander of the 6th Army in Barbarossa, and a ragingly enthusiastic Nazi), or the acquiescent criminality of Guderian or Manstein (well regarded and decidedly not-Nazi generals, who nevertheless did absolutely nothing to hinder, and even encouraged, the mayhem occurring directly behind their lines).

Rommel openly disregarded 'leader orders' from Hitler stipulating the execution of PWs of certain categories, and offered robust protests over brutal Italian suppression of insurrectionist local populations which were standard practice for contemporary German/Axis forces (i.e. massacring innocents).

To reiterate: this was not due to an excess of compassion for human life. The reasoning behind all this was entirely pragmatic and common-sensical. To demonstrate I'll quote some passages from his memoirs that will hopefully illustrate for you what I'm saying:

I now occupied myself for a short time with the prisoners. Among them were several officers, from whom I received a number of requests, including, among other things, permission to keep their batmen and to have their kit picked up from Philippeville, where it had been left. It was greatly to my interest that the Philippeville garrison should surrender quickly and without fighting, so I granted the requests.

Rommel does not tell us "I spared these defeated men and treated them well because I did not care to be haunted by by their blood on their hands, and the wailing of their orphaned children in my dreams", rather, by securing their surrender on decent terms he saved himself a lot of time and difficulty, and made his job a lot easier. His account of his dash across France (which made him famous) contains numerous occasions on which he used captured soldiers as negotiators, sending them ahead of his attacks to demand the surrender of this-or-that enemy unit. Sometimes it worked, sometimes it did not (and when he encountered a particularly stubborn commander who he felt resisted longer than necessary he liked to berate them for causing needless casualties) - I feel it should be obvious that it is entirely preferable, in purely military terms (as opposed to moral), for one's enemy to give-up without a serious fight. That this truism was essentially and systemically ignored in the USSR was one of the biggest reasons for the failure of Barbarossa - initially Red Army soldiers surrendered in huge masses, but as word spread of their fate in captivity (almost certain death), resistance stiffened immeasurably - but I digress. That Rommel was not exactly the bleeding-heart type is demonstrated by the fact that he had a French officer summarily shot for ignoring an instruction to retire obediently with the rest of his captured men.

I wont go into great detail about the WWII German penchant for mass reprisals against civilian populations in occupied territories which featured partisan activity, other than to say it was extremely common, to the point of being codified for the invasion of the USSR in the so-called 'jurisdiction order' (I invite one to Google this). Again, I'll let Rommel speak for himself, relating some incidents from the fighting in Africa, firstly regarding the activities of British commandos:

They tried again and again to incite the Arabs against us fortunately, with little success, for there is nothing so unpleasant as partisan warfare. It is perhaps very important not to make reprisals on hostages at the first outbreak of partisan warfare, for these only create feelings of revenge and serve to strengthen the francs tireurs It is better to allow an incident to go unavenged than to hit back at the innocent. It only agitates the whole neighbourhood, and hostages easily become martyrs. The Italian commander shared my view, and so the occasional Arab raid was usually overlooked.

And when Italian troops committed 'excesses' against Arab civilians:

As a result of Italian loss of prestige after Graziani's defeat, a number of Arab tribes had begun to get restive. This was not helped by the fact that Italian troops occasionally took liberties with the Arab women, a thing which Arabs particularly resent. I was forced to send an urgent request to the Italian High Command, asking them to see to it that the Arabs were treated with sufficient respect to avoid an armed uprising close behind our front. At about this time officers and men of the Trento Division were responsible for several excesses against the Arab population, with the result that the Arabs killed a number of Italian soldiers and kept the Italians away from their villages by armed force. There are always people who will invariably demand reprisals in this sort of situation for reasons, apart from anything else, of expediency. Such action is never expedient. The right thing to do is to ignore the incidents, unless the real culprits can be traced.

So what he is saying, is that reprisals only make things worse, by encouraging further resistance that would detract from efforts on the frontlines, against conventional fighters - it seems very likely that had the "real culprits" been identified he would have dealt with them with the utmost of severity. He does not tell us that "taking liberties" with Arab women was something he found morally reprehensible, but that it pissed-off the local communities and provoked violent resistance, and this was counter-productive to the prosecution of their war - the "right thing to do" is not 'right' from a moral view, but a military one.

Rommel was really, in my assessment, an amoral and apolitical figure, an ambitious military professional and utterly obsessed in a Jungerian sense (author of Storm of Steel) with combat and battle. He was one of the foremost exponents of his art, like a gifted and driven athlete, and the war was his Olympics, and it seems that his cause and his masters barely entered his calculations until he had missed his shot at the gold medal. He served a beastly regime, but is only tangentially responsible for their crimes (if the rapid defeat of France set in motion the worst excesses of the war, he was significantly responsible for making it happen) - you are welcome to judge him unkindly for such, but in context, and compared to his peers, his behaviour was relatively upstanding.