I just read all the posts. You have tons of good advice on the food, water, meds. calming diffusers and etc.I am glad so many people weighed in. Don’t feel bad about baby sitting. All cats are different and he just as easily could have loved company. I get a rainbow of cat reactions here as I bring in new rescues. It is a balancing act for sure but I think a lot has to do with the personality and history of a cat. I can only tell you what I do in case you are faced with another cat. I will also get to how I treat my nervous kitty. You can either read through or just skip to the part that is most relevant to your current situation. I hope something here may be useful. I start by putting new kitties in a separate space from the others. The cats already established here seem more curious about and sympathetic to the new cat if that cat is not allowed to run freely through the house. ( that restricts germ spread so it is required here for a time anyway) The free cats tend to try and get close to the “hidden” cats. They sniff the door, put their paws through the cracks and any other thing they can figure out to do. Movement that is slightly hidden to a cat is far more intetesting as a puzzle to them than seeing everything immediately. Curiosity! The more I tell them no, the more determined they are to get their way. It becomes a game. They also feel a need to release the prisoner. My cat Mackie can open doors so I have to watch that one. I keep the kitty who is quarantined happy with toys and attention until I feel it is safe to let them out. First they must be healthy but also I want to feel that the others are curious and, hopefully, ready to meet the new cat. It does not always go smoothly. Some kitties change their minds and want me to put new kitty back. Not happening. I give ALL kitties their own safe haven. Cage, carrier, cat tree with hiding place or any spot I have available. With most I try to give them a door that can be closed. Some know how to close their own door. Don’t sell them short. They are every bit as teachable as another other animal residing with humans. Locking is only done out if total necessity for health, travel or safety once a cat is in the general population. All cats have their own food , boxes and water. Each cat has toys but there are also shared toys for those wising to share. Arguments and tension occur. I handle this by separating the participants. A gentle but firm,”no” to both parties. Then I take each one to a quiet space , one at a time and top ranking cat first. I give them petting, holding, brushing, calming speech and relaxing things only. No excited play or extra stimulation. The idea is to calm kitty to a mellow and relaxed state to remind them that I will keep them safe and secure. I try to act as House Mom! Lol when kitty one is relaxed I leave them in their quiet space and move to the next cat to do the same thing. Cats do have a bit of a pecking order or will try to establish one with new arrivals. Very stressful! A permanent resident needs to know they will not be losing their spot. Reassurance is so important! The resident should always be attended to first. Like ranking officers. Fed first, petted first, played with first and reassured of their place in your heart. It may seem harsh to the others but as long as you love them all equally it works. If you have kitty visitors that are tame and temporary you might consider visiting, feeding, etc. in totally separate area unless you know your kitty wants them to join in. Sensitive and nervous cats are harder to get acclimatized. It takes more time and much patience. It can’t be forced. Some cats never like each other but so far I have found that they do respect boundaries. I stick to my reassurance methods. It seems to settle things unless something specific causes a disagreement. I did have one male that developed a problem and was urinating in bad places. I had him checked by a vet but he was healthy so I started giving him lots of extra, private, attention. I took him in a bathroom and shut the door for quiet time together. He got the luxury, cat spa treatment. No exciting play stimulation during this time. All the relaxing things mentioned here and in other posts were applied plus a sort of kitty/petting version of massage on a soft blanket in my lap or the floor in front of me if he wanted to stretch out. I tried to make him understand that he was the most important thing in the world to me. He got my complete focus. I do make it a point to talk to all the cats. We all give dogs credit for understanding words and tone of voice. Cats do too. (His entire family had died, one by one, finally leaving him the only survivor. He was still young when this happened and he became very clingy. He is a black/ Siamese) The spa treatments continued for about six months before he finally stopped his nervous urinating. I also took him to a secluded litter box often while petting and encouraging. At first he seemed to want me to stay while he used the box but he didn’t need the reassurance for long. Then he just enjoyed the ride. Lol He hasn’t urinated in the wrong place since. This took time and patience but it was well worth it. Will he do it again? Possibly. If stressed it may well happen but I am prepared. I try to ward off the extreme reaction by giving extra snuggles and some private time but I don’t have to devote the intense level of treatment that I did in the beginning. I do find that a sensitive time is with new arrivals, although he is often my first greeter now, and during thunder storms. I make sure to remember Purryman at these times. I find him and pick him up for a few whispers of love and some snuggles. As I said before, every cat is different but putting out those deep loving vibes and tender snuggles have kept peace in my house. We all know our cats kind of dominate our lives because they are so important to us but if a kitty has worries, make sure he knows that when he needs you to be in charge of the bad things in the world or other cats, you are really the top cat in the house. ( with the exception of him, of course!) Sorry for the length of the post but it’s hard to explain what I do in a few words.
I hope he relaxes. I’d love to read a new post about you both feeling good, calm and happy. 
I hope he relaxes. I’d love to read a new post about you both feeling good, calm and happy. 
Now that you pointed it out I am giggling too! 
