Well if it’s eating and drinking and pooping then it is doing better! I’m no good at splints, never made one before, but just search it up and you should find something telling you what to do!
I’m sorry about everything you are going through right now, and I understand the feeling to want to do everything you can to save it. But unfortunately that is a bit of a selfish act sometimes. Like @Wyorp Rock said, putting it out of its misery might be the best option, instead of wanting it to...