Wow! You have been through a lot. We have a behavior forum where you can post about the biting. Also, some shelters may spay for free, or maybe a little, if you can't afford it.
I wanted to say "Welcome" and I'm off to read your thread in the behavior forum. I've had some experience with biting kitties, but I want to read what others have suggested before I chime in.
Regarding the spaying, there is a group called Alley Cat Allies - and they are all over the country. Let me know if you can't find a link and I will find one in your area. You can PM?