I don't think you're a monster -- I think what you're doing is noble and deserves recognition. Often I have had to be a supportive friend in difficult pet health situations, so I absolutely know what it feels like.
However, I do question why you refer to Toasty as "it". I understand you're trying to distance yourself to lessen the emotional impact. However, if it were you taking care of her grandmother in her final days, would it be acceptable to refer to her as "it"?
I also do have to question why the final step is shooting the dog. I could see if you don't have funds for euthanasia, however there are a fair number of clinics and shelters out there that will do a free euthanasia if you explain the situation. I understand if that isn't feasible but I urge you to consider euthanasia.
Either way, I'm glad he's being taken care of in his final days. It's what every animal deserves, and it shows you care on some level, even if you are trying to deny that feeling. I hope you can both find some easing of tension in this incredibly stressful situation. Thank you for caring.
This video got me about a year ago. Nothing super graphic, not at a slaughterhouse, not even any abuse. But the "simple" act of taking a newborn child away from their mother completely shattered any remaining dissonance I had about going vegan, personally.
https://www.youtube.com/watch?v=iL9QJEm_SJY
I will echo the other commenters suggestion to get some vegan creamers. Honestly, it may be worth considering cutting them off if they can't follow your rules in your own residence. There's plenty of food to eat that isn't meat (obviously); there's no excuse for them having meat delivered. If they can't go one week (not sure how long they're staying) without meat/dairy in your house, then they honestly don't care about your feelings.
I would ask them what foods they would prefer -- give them options like tofu, different beans, lentils, edamame, etc. Maybe make a soup with their chosen legume.
I would encourage you to compromise and """allow""" them to eat non vegan if you go to a restaurant. I understand this is really distressing, but with some people it can be helpful to focus on one goal at a time (e.g. no animal products in your residence).