First of all, that is a BEAUTIFUL reduced pattern bp you have there
I know exactly how you feel. I'm an animal lover too (although I completely agree with you about Homo sapiens), and my ball python absolutely refuses to eat frozen thawed. My corn snakes are more or less eating machines and will eat anything you put in front of them, but my girl will have none of it. And although I don't really care for mice personally, I still feel a twinge of guilt every time I buy one and drop it in with her. I just try not to think about it and tell myself that I love my snake more and she has to eat. But still I do feel bad, and my family doesn't help when they're always asking me "how can you do it?" and "oh that poor little mouse" etc. I really never want to have to feed her rats...that's going to be tough.
So yeah, you can try to switch him to frozen thawed. It is probably better in many ways...but if he's been eating live mice his whole life, it might be difficult.
I agree that you shouldn't feed him in the bathtub, the shower curtain being the main reasonI feed all of my snakes in a separate container (sterilite) just so they don't accidentally ingest any of their bedding, but you can definitely feed him in his enclosure too. If you do have to feed him live again though, make sure to remove any decorations from the tank so they don't get in the way.
Good luck, and I hope you can convert him to f/t. You really do have a nice snake there regardless. Just know that you're not the only one who feels bad about feeding live. Sometimes it ends up being a necessary evil though unfortunately