He's doing good so far! He squirms when I have to do the antibiotic injection, but otherwise doesn't react. I also had a hell of a time getting him to take the oral medication for his tapeworm. He refused to open his mouth and I was concerned about harming him, but he eventually gave in. He's been super docile through this whole thing.
He's got one more injection left and also one more dose of medication for the tapeworm, then I'll wait and get one more fecal test done.
The vet clinic had to order the tapeworm medication in specially for me since it's apparently very rarely needed for captive snakes.
There's been zero change in the size of the bump on his head. I think at most I will get an x-ray done next time I take him in, but I might not go for the surgery option to get it removed (really depends on $$$, you know?) as long as it doesn't seem to be harming him. He'll just be my funny-looking snake.
Thanks everybody for all the support and advice!