I am glad Blue has been treated. Hopefully his wounds will heal properly.
I agree with another comment suggesting you get the details of the dental surgery in writing. They should also be able to tell you the urgency of the situation. I'm sorry to hear that the costs are so high and wish I could assist more. My wife suggested asking if the vet clinic can do a payment plan.
My final thought was that if your "dad" really doesn't care about the cat and is just using Blue to get attention (perhaps he hopes something will happen to him so he can go "Woe is me! Somebody killed my cat!"), then it might be best if you are able to rehome him. He seems like a lovely-natured cat and you clearly care about him a lot; if your "dad" is going to deliberately harm him (or allow him to be harmed), though, Blue may be safer in a new home. I hate suggesting lying, but since Blue has already been attacked you could arrange for him to get outside and "disappear" if you need a way to avoid your "dad" finding out you rehomed "his" cat.