I am so sorry you are suffering. Your sweet kitty just acted as many a pet might. He was not being mean, did not mean to hurt. I can see he means a great deal to you. Would you have a room or a closet you could make a space for him with a screen door. He would be still be part of your family but have a space you could put him where he could be secure.
I take this happened at night, he could be put in his own space at night or when you leave the house to prevent further accidents.
As far as the other, there will always be those who take advantage of any one they can. Always best to get everything in writing and signed, dated, detailed cost. Text and email are not always the best way. Also, I never pay for anything before the work is done and completed to my satisfaction.
I wish you and your husband well!