the boiled chicken breast helped harry a lot. now it's not his main meal but i use it as a treat to help solidify his poo, too. gotta get your cat back on cat food soon, but boiled chicken will be fine for a week.
any vomiting since this? i worry between the vomiting and diarrhea your cat wasn't getting enough nutrients. oh, and it's fine to give him some of the water the chicken was boiled in. that'll help somewhat with the dehydration from the diarrhea.
many vets will try the flagyl route next (for 7-10 days), so you might want to ask your vet about that. this could be just a temporary reaction to the food that disagreed with him, so give yourself a big hug from us, and your hubby too.
oh, and just FYI, never stop food for a kitty. without food for over 24 hrs many cats develop a serious condition called hepatic lipidosis. cleo got it from vomiting for a week even tho she was still eating (because she wasn't getting enuf nutrients). so trying a bland diet will help or even chicken baby food (nothing with onions or garlic).
some cats have a reaction to fancy feast because of the flavor enhancers they use. so it might be a matter of finding a different food. wellness grainfree chicken or wellness core canned food (chicken & turkey mixture) is a high quality cat food tho it might be harder to find in your area. it may just be a matter of trying different store brands til you find one that doesn't aggravate your cat's gastrointestinal system. if you can find wellness and you join their website, they offer coupons linked via email. usually i get $3 off any wellness dry food (one of my cats eats dry because she has cancer and i have to give her whatever she'll eat), but til july 12 they're offering $1 coupons for canned food. you can xerox the coupons you print from their email offer for a substantial savings.