Jenna
Pleased to hear things are going well for you and Heathcliffe, and that you are having him microchipped. Just a thought about cats and collars. Can you slip two fingers under the back of the collar, and gently pull it off over his head, it is vital that if he gets caught up in anything that he can pull his head free from the collar. This is one of my worries about collars, after seeing a huge, magnificent ginger tom cat hanging in a hedge, quite dead, strangled by his own collar. It haunts me to this day. I did find the owner, and took him home to a very distressed lady. If you try the removing the collar test as described above, he should be OK. My three are all microchipped, but don't wear collars. I wish you much happiness with Heathcliffe, he landed the right way up on his four paws when he found you. I'll be thinking of you.
Good Luck