Thanks for the suggestions, I've tried adapting his routine to include them but it hasn't gone well. The vet said that the ultrasound ruled out any inflammation and the lining of the bladder looked normal so he said he can almost rule out IC.
He won't drink plain water (and I would figure raw meat had enough moisture in it) and he drinks all the water that comes off the meat when it's defrosted. I also give him little bits of catmilk just to make sure he's drinking. I can't think of any other way to get more water into him.
Is the protein in the urine normal and something not to worry about? Is he eating too much? Too much protein? He's 10.5lbs (ideal weight for him) and hasn't gained or lost any through all this. The vet seemed most concerned with his specific gravity and neutrality of his urine. Is there anything I should be looking at and watching or are the slight highs not enough to worry about?
In regards to play, he has my other cat as well as at least 30 mins/day of play time with a human. He has always gotten supervised outdoor time (no new visitors in the backyard) and has plenty of windows and doors to look out of (about 30!).
I tried feliway diffusers and concentrated spray but he peed near it and aside from the first day, didn't seem to notice it. I currently have a sentry collar (pheromones) on him and am hoping that might help.
Nothing has really changed in the house that would cause this and everything has been watched carefully to try to get this to stop but he keeps going.