If Edward VI were to survive his illness and ruled as long as Elizabeth did, that means he would rule 45 years. Thus, this makes him die in 1598.
Likely suitors for Edward VI would most likely be a Protestant Princess. My guess would turn either towards a Protestant German princess (like a Saxon), although I would tend for a Danish or Swedish one. In the timeline All Hail Germania, I remember ImperialVienna had married Edward VI to a Vasa.
Two other possibilities would be a Hapsburg or a Valois as these are the two rival Catholic Nations. However, I'm not sure it would happen : the Hapsburg were a bit arch-catholic while the Valois are French, the worst kind of men for an Englishmen at the time.
Edward VI was fianced for a time to Mary Stuart, but the Queen of the Scots was already married to Francis II of France by the time Edward VI fell ill. Of course, she could be married to Edward VI when she returns to Scotland after the death of Francis II, but that doesn't seem likely.
One last possibility would be for Edward VI to look in England : it's less prestigious than another princess, but he could marry an English noblewoman. Among these possibilities, there could be his cousin Jane Grey (they were the same age).
The Question of Mary & Elizabeth is a very interesting one...
Mary is 37, so it might be a bit late to marry her. Plus, her bloodline technically comes next after that of Edward's, so I don't think she would be married : her Catholicism makes her a risk for the English Protestants. She might convert, but I think she was too Catholic for that.
As for Elizabeth, I don't have a clue. She is currently 20, so chances that she would marry are high. I don't have a clue on who would be her future husband.
English Protestantism will be harsher than it was OTL. Edward VI was far more Puritan than his sister Elizabeth : Anglicanism would probably not just be a copy of the Catholic Church with the King serving as the Pope (it's basically that OTL apart from one or two differences) and have more Lutheran or Calvinists roots.
As for Edward's ability to rule, it seems Chroniclers showed him as very clever individual as well as someone very able for his young age. He could probably overshadow his father and grandfather and be the greatest monarch of England ITTL. It would be interesting to see how he deals with the Religious Wars in Europe, most notably on the other side of the Channel.