So sorry to hear about the poor hog. Sadly, especially with wildlife, not all of them make it, however hard people try to help them. I am sure you tried your very best for it. It’s always incredibly sad when a hog dies.
Have you, or have you considered, working with an experienced hedgehog carer/rehabilitator. You could learn a lot from them, and they might be able to help you with some of the questions you have. I imagine it is almost impossible to start this sort of thing up on your own, without the knowledge that someone who has already been doing it for a while has. It is great that you want to do this, but maybe you would benefit from some sort of backup in the form of someone more experienced.
It is really difficult for anyone to answer this sort of question with so little information and if you had another local carer/rehabilitator you could ask, you could give many more details than is possible on here. Just a thought.