Whoa, more very good questions and suggestions -- THANKS!! 
		
		
	
	
I've tried raw chicken, egg (raw and cooked), rare roast beef, and most every other thing you can try to tempt a cat. (As well as, to date, six different brands of dry food and five of canned). If he is eating, he will eat anything; if he is not, nothing. The chickens are getting a good deal out of this anyway 
 
He 
does throw up, a lot (like every 4-5 hrs, sometimes as often as every 1-2 hrs for half a day or so), during the times he is not eating. (not at all when he is eating ok). It starts out as clear liquid but progresses to blood-tinged as the hunger strike goes on. Is accompanied by nasty wet squirty diarrhea and drinking a lot. I have no idea which of those three things (vomit, diarrhea, drinking a whole lot) is cause and which is/are consequences, tho.  He is currently on famotidine and two other pills (an antidiarrheal and an antiemetic, don't recall names offhand); famotidine has seemed to help some, the other two seem to help a lot. The antidiarrheal and antiemetic are just short-term til he is solidly eating again. He's been getting the famotidine for at least a couple weeks after starting eating again. I don't like using lots of medications but these do seem to be helping so will continue as vet directs for now.
WBC count was just towards high end of normal, remember, not elevated in the usual sense of the word.
Megacolon and IBD have been considered hard (as they were the vet's initial theories) but everything looks normal on xray and u/s, no thickening of gut wall or distension of gut - but it is uniformly filled the whole way with nonechoic (i.e. thin non chunky) liquid. 
He ate about half his normal breakfast this morning. Not sure whether this is part of return to normal or whether yesterday was an anomaly and he's going back to not eating. Argh! 
Have to get new bag of catfood today anyhow, so I will see if I can get his #s.
(edited to add, b/c I forgot to say: only two houseplants in the house, neither has been chewed at all in any way. You know, I'm not sure whether his temp was taken by the vet [not while I saw, but he was there for the day several times, so dunno], I didn't take it, that is another good point. I may try to take his temp if he starts acting poorly again -- but am not sure whether it will work as, despite his generally very relaxed and confident personality, he really *really* does not like to be restrained and have things done to him, and the one time I did see the vet try to take his temp, the vet gave up 
)
Pat