I don't think there's any easy answer on this one. I, for one, would not and could not tolerate pee and poo on my carpet. I know there are people who can, and they may shame me, but I just can't live like that.
Maybe if I tell you a bit of my story, you'll feel better. I adopted Sampson on 5/15/05 and gave him back on 5/18/05... because he was sick and peed on the carpet. I felt the same way as you did, it was too much. I had lost my other cat on 5/11/05 and yes, I probably jumped too soon into getting another one, but like you, I thought I was getting a healthy cat. I brought him to the vet the next day after I got him because he was pooing blood
The vet told me that he wasn't sure what it was, but I should bring him back for more tests. I wasn't prepared for this. I had just spent countless $$$ on my last cat. Having to pay for a checkup of a new cat or neutering is one thing, but gosh I didn't want to go into the visit and research deal again... but I did keep him and tried to decided what to do. He continued to poo blood, and I was giving him medication and on the 4th day I had him, I noticed he peed on the carpet
I know, I felt bad too, like you, but it was all I could take. The pee wasn't such a bad thing, I think maybe I could have worked with it, but it was the "unknown" of the medical too.
Anyway, to make a long story back I took him back to the shelter that night and cried the whole way. Well to my surprise, the shelter was extremely apologetic for adopting him out being so sick. I found out that he had coccidia and round worm, and a bad URI. I continued to miss him, and went to see him at the shelter almost every day. He was so sick in his cage, I felt terrible. Well once he started to get better, the shelter asked if I was interested in adopting him again, I was shocked!!, as I thought for sure that they woud be extremely mad at me, but you know, they understood. So I waited a bit and I did re-adopt him
He's here with me now since Monday and he's doing fine. I think his pee incident was due to stress and probably being sick, and possibly me having the one litter box in the back bathroom. I now have two litterboxes for him, one in the kitchen, and one in the front bathroom, LOL!! He uses both!!, LOL!!... but I'll pull one eventually.
Anyway, my point here is that you can only do what you can do. I think there are people who are prepared to deal with sick cats, and maybe people who are more able to have cats pee and poo in their house and it doesn't bother them. There are others that it does.
So if the cat is sick, and he is wrecking your house, then I would give him back
I know it's horrible, but what are your other options.... I personally couldn't have a cat peeing and pooing in my house. If that makes me a bad animal lover, oh well... but that is what and who I am.
So you can either take him to the vet and try to determine if he is sick and maybe his peeing and pooing is due to that, or you can send him back. I think his meowing in the room would go away eventually as that is just stress of him getting acclimated to your house.
In anycase, please don't feel bad... we do what we can with what we have and that's all we can do. You obviously are good mommy to your other cat, so you're far from a horrible person. It's just a bad situation to be in, and unfortunately isn't going to be one that will be resolved easily.
Good luck... keep us updated as to what you decide to do.