I am unable to donate at this time, but I just want to say that I feel for you. My cat Max, who looks almost the same as your Arthur, had the same problem where he needed emergency surgery in the middle of the night and now needs special food to prevent the problem. It was one of the most stressful nights of my life, and I can't imagine how you are feeling with it happening more than once.
I am sending all my hopes to you, Arthur seems like a good man