oh Lisa, i am so sorry to read this, he is so young, but i am sure with the love and expert care you give him and advice from your vet Willy will live a long life, i went through it all with Ash, but then he was an old cat, and he was on steroids, which may or may not be suitable for Willy,i wish you and Willy all the best and i hope he will continue to do well on his new diet.,thinking of you both. HUGS.

P.S as for SUB Q'S i would discuss this fully with your vet first.