the other Charleses weren't Catholic - II did convert on his deathbed but I was an Anglican with a Catholic wife and a distaste for Puritans. However, they're not seen as the finest flower of the British monarchy, and rumour has it that Charles would take his grandfather's name as George VII.
I don't think he'll step aside. Waiting for the throne is the only job he has; and it's the source of all his influence too. If he sttepped back he'd just be a dowager duchess of no importance.
Of course he won't step aside, it's his destiny, anyone who thinks he'll step aside wants their head read. King George VII and Queen Camilla are comming!
He wouldn't be the first to use a regnal name which is not the name by which he was known. Edward VIII was known as David to his family and friends; David was one of his other baptismal names. King David ? Nah, too Jewish! Charles would not be 'Catholic' but it would not be a good omen; the First was executed after a war against Parliament and the Second's most notable achievement was hiding in an oak tree! He has plenty of names to choose from.
The wife of the king is a queen,,,
The consort title was given to Price Albert by Victoria but Phillip isn't Prince consort but is a Prince of a royal house in his own right. (albeit a minor house of deposed royals)
There is nothing unusual about a monarch adopting one of their christian names as their regnal name other than the one by which they are usually known, e.g. Victoria (Alexandrina), Edward VII (Albert Edward), Edward VIII (David), George VI (Albert).