While many people have later stated that Edward was a "sickly" child, those are statements made with the benefit of hindsight knowing he died young, before reaching his sixteenth birthday. While he was not as athletic as his father, there is no evidence that he was particularly sickly until he fell ill at the end of 1552 which suppressed his immune system and left him prey to the illness (probably tuberculosis) that ultimately killed him in July 1553 (with help from the toxic medications his doctors gave him trying to cure him -- and/or trying to keep him alive long enough to suit his Lord Protector, the Duke of Northumberland).

As for Mary, by 1544 (when she was restored to the succession), she had made submission to her father and he believed she in line with his Henrian Catholic plans. She certainly was still a Catholic at heart -- and, at his heart, so was Henry, just without submission to the Pope. There is nothing in the Scriptures that requires submission to a centralized authority to be a good Christian.

What Henry did not foresee was that his son and his Anglican Church would be so dominated by Protestant, reformist factions so soon after his death.

(As a completely irrelevant side-note, my interest in history was kickstarted at the age of 12 watching a not-very-good historical movie, Young Bess, about the youth of Queen Elizabeth. Charles Laughton reprised his role as Henry from "The Private Life of Henry VIII" and got to do Henry's death scene. On his deathbed, Henry mutters a very Catholic request for people to pray for his soul to spare it from Purgatory. His brother-in-law Edward Seymour leans down and pats him and reassures him he's safe since he abolished Purgatory (which, to be fair, was a pretty late addition to the Catholic afterlife belief system). Henry just groans "Don't argue, Ned". I've always found that a beautiful illustration of just how mixed up everything was at the time.)

There are a few things I want to address:

1. Edward VI of England was never sick as a child. What we know from diaries is that he loved playing sports, attending Church and learning things. It was until later, after his father had died in 1547, where he began to be really sick. It is a huge misconception amongst viewers of this History.
2. Henry VIII loved Catholicism. We can see this through his actions. Henry defended Catholicism when it was being tested most, when he wrote a polemical text which was a rebuttal Martin Luther's 1517 95 theses, in which Henry's Defence of the Seven Sacraments earned him the Title 'Defender of the Faith' by Pope Leo X -- a title that is still etched on ever English coin in 2021.
3. And you are right, the Henrician Church of England was rather laxed in regards to Catholic acts, but that was later. The issue was is that Henry gave the reigns and all the power in regards of reforming the Church to Thomas Cromwell, Vicegerent of Spirituals, and it is safe to say that Cromwell was a Protestant and was a follower of Luther. From that we see the executions of key, prominent Catholic figures such like: Thomas More, Elizabeth Barton, Nun of Kent and John Fischer, and more. We see the radical changes, such like: the Translation of the Jeromian Vulgate Bible into Middle English, the passing of the Oath of Supremacy which forced everyone to take an oath pledging that King Henry VIII was the Supreme Ruler of the Church Of England, and also legislation like the Ten Articles and the Bishops Book (1536) which completely altered the Church's processions. There is also the mention of the Dissolution of the Monasteries (1536-39) which a lot of people question why Henry would do that, simply money. Henry bankrupted England. He spent all of his father's coffer money, which there was around £2,000,000 of, on the 1512-14 Wars with France which were pretty much uneventful, and also a lot of money was spent on his grandiose lifestyle. Henry was called the 'Renaissance Prince' for a reason, he detested the laborious work of a King and shuffled that out amongst his advisors, namely Bishop of York, Cardinal, Thomas Wolsey, and he would rather focus on hunting, other sports, and boasting to others his wealth, for example the 1518 Field of Cloth of the Gold was an absurd Anglo-French get-together to see who was the best ruler. Henry spent 1/3 of his wealth on gold to place around this 'party' and him and Francis I, King of France wrestled -- the latter won. Henry did it merely for money, the dissolution of the monasteries, he also did it to obtain 1/3 of the land which the Monastic Lands had held for some 900 years. It is interesting reading Cromwell's reports of the state of the Monasteries. Cromwell was put in charge in 1536 of the Valor Ecclesiasticus that is the estimating the wealth of the monastic lands. Cromwell sent two people: Richard Layton and Thomas Legh to survey all Monasteries, but to do it so deviously to make it look like the monastic lands harboured awful secrets. They lied about the drinking, the sex, the drugs, etc. Homosexuality too, which was seen as sinful in the 16th century, was exaggerated [120 cases, only 12 have been seen as true by Historians] and that was the catalyst to push Henry VIII to go through with it.
4. At the end of his reign, the Henrician Government will have this so-called 'counter reformation'
   1. We will see the 1540 execution of Thomas Cromwell. Was this done for religious purposes? As we know Cromwell was tasked with setting Henry up with a new wife after his, as he saw it, 'his only true wife', Jane Seymour, had died during childbirth and Cromwell chose Anne of Cleves. To be clear, this attempt of a marriage was totally religiously-based. Cromwell chose Cleves, a staunchly Protestant area of the Holy Roman Empire. Cromwell almost wanted the marriage to symbolize a Protestant coalition against the Catholic states surrounding them. As we all know, Henry and Anne supposedly met on New Years' Eve and Henry was disgusted by what he saw, annulling the marriage after months, marrying the very young Katherine Howard. Cromwell's execution will also play in with the fact that Henry's inner-circle hated him. Henry's right-hand man throughout a lot of his reign was Thomas Howard, 3rd Duke of Norfolk, a pious Catholic but was sympathetic to Henry and the actions he needed to take to get that annulment from Anne Boleyn in 1532. Thomas Howard will come to detest Cromwell because of a Thetford Priory, the Priory of the Howards, in which Cromwell forces Thomas Howard to dig up the corpses buried in the ground and to move them elsewhere before dissolving the Priory.
5. Also, Henry will reverse a lot of the Cromwellian, Protestant reforms. The Ten Articles (1536) will be reversed by the Six Articles (1539), Henry will pause the Great Bible (1539) which aimed to get one translated Bible into every parish in the country, Henry will pass the King's Book (1542) which directly reduced Protestant roles within the Church, laid out by the 1537 Bishops Book.

In my opinion, Henry was always Catholic. He was a staunch believer in Roman Catholicism, only reforming the church as a conduit to his own selfish wants.