Sorry to here you mut is in a bad way I know how difficult it can be and I hope he pulls through OK.
Shop around for insurance there are loads out there from Argos to Asda,read the small print for ongoing conditions etc. we have just paid out £800 for a scratched eye ball. our Nellie is always in the wars Also most medications can be purchased from some chemist (we use Manor) cheaper than the vets.
Do all you can for them as they do for you but don't let them down when the time comes to do the right thing.