at wits end..

I have two cats. Two cats who as of recently have special needs. We've had them since 2001. Up until now, we've had the minor issues every cat owner has put up with, but now it's getting out of hand. Tabitha, my fat cat pukes constantly. She's been to the vet many times over the course of 7 years and they just think she has a slower digestive system. Which means she vomits when she eats too much, and it can only be fixed with medicine. Medicine that a) I can't afford and b) I can't touch when I'm pregnant since it's a trans-dermal. (transfers through skin)
We've had MANY puking incidents in the past month and a half so I've been dragging out my steam cleaner almost daily, or at least 4 times a week. Now with having 2 kitties, I feel bad assuming it's Tabitha, because we rarely catch her in the act of puking, so it very well could be Digger. --- But Tabitha has an issue with psychogenic licking and licks herself bald in spots which means extra hair going through a digestive system that is slow.
**note -- we buy all of the expensive cat food from the vets office with no dyes, etc., so it's not that we're buying the "crappy" (or "normal" if you ask me) kind of food that sometimes upsets kitties tummies.
So this week I plan on taking both kitties to the vet AGAIN to rule out anything else.
Oh, and their new thing this past month is pooping outside of the cat litter box. They've done this one time before, when there was only one box for the two of them. To alleviate this problem, we upped the number of cat boxes to two. When they started doing it again, we decided to get a 3rd cat box. We empty the cat boxes 3 times a week, so it's not a matter of having dirty boxes either. Oh, and we've changed their litter from regular cat litter (arm and hammer scoop) to a new kind of wheat litter recommended by our vet. All three cat boxes are in one room which we have dubbed the "kitty room."
We call it the kitty room because they have destroyed it. That's the room where their food is, and all 3 litter boxes, and where they poop on the floor.
I'm truly at my wits end, to the point where I think my life would be a lot simpler and stress free if I found them a new home. A new home that can deal with the stresses they cause. Right now, I feel like I live in their home, and not my own. I hate how my house smells, no matter how often we change the cat box, and I hate that when I come home, there's always certainly cat puke somewhere..
My sister-in-law thinks we're cruel for wanting to discard our cats, since they've lived with us most of their lives.. and believe me, I cry when I think about it. It's kept me up nights for the past few weeks, and I feel so guilty for even thinking about it. I love my kitties, I'm their mommy, but I can't take this anymore.. I truly am DONE.