Have you checked your local humane society to see if they have a low cost neuter/spay clinic for low income families? I know ours does.
Also you mentioned the chomping down on the neck that Billybob is doing to Baby. I have to tell you that Sweet Pea does that to kittens (including hers) and to the love of her life, Jasper. Not sure why they do it but it is always during grooming sessions with each other. It was horrifying when I saw Sweet Pea do this to one of her kittens, I thought she was trying to choke it, but the kitten loved it and stuck around her
. Now I just ignore it.
Is there true fighting (hissing, growling, raised fur) when this happens between your kitties?