Isn't this a case of take your own advice?
Many instances have already defederated lots of stuff. If you feel strongly about that shouldn't you migrate there over asking other instances to do the same thing? Seems like if he wanted to he would have here by now.
All just feel like fediverse problems and IMO the action should be take ~2 weeks off line and then evaluate there all the shit lands and decide. In thedude's shoes, I would have already pulled the plug on this as way to much hassle to get into the middle of. Props to him for not.
What does it actually cost? I have no basis for a ballpark guess even. I've seen this question asked to a number of admins and haven't seen a direct answer.
It's hard to judge how sustainable a donation based approach is without that info.