I have no experience in this type of situation. Julie has gotten a little carried away and left some pretty good gouges and scratches, until she learned to keep her teeth and claws to herself...but she also is the only cat. Our dog is older and doesn't bother her so she has free run of the house.
I'm wondering...as PIF suggested...if you have a room in your house that you could set Magoo up in so he could be out of the cage but still segregated until he gets acclimated? Since he was stray he wasn't used to the caging...but with his surgeries and such he has been in 'recovery mode'. Perhaps now he is feeling more himself and wanting to get out and about.
Good Luck and don't get discouraged...time will help I'm sure.