If there are still maggots on the wound, try to take them out with a tweezer.
Hi Tommy,
Taking him to the charity vet is the best thing. They can actually look at it, test it and advise you as to what needs to be done.
I am sure they will have a payment plan for you to pay off the bill over time.
If not, do you have a veterinary school near you? They can also help you, as they are a teaching hospital and these kinds of cases are a learning tool. I am not sure they even charge.
Think your kit will need amputation, which he will be fine with--many cats lose parts and keep on ticking.
Good Luck and please keep us posted
CML