Looking for some advice.
Long story for full background.
My older cat is 6, he's always been very laid-back if a little aloof. He'd mostly sleep at home, would let us pet him on his terms but not particularly a lap cat and would often go out.
We recently got a new kitten which obviously is a big change for him. We introduced them slowly with scent swapping etc and although not keen and not really interacting with her he was much his usual self and was going out but still coming home every day.
After a couple of weeks he disappeared, we know he visits a few houses locally but don't know where. I posted on SM and knocked doors etc. He's now reappeared thank goodness 2 weeks later. He's packed on a lot of weight so obviously has been being kept in someone's home and being (over) fed.
The big issue is he seems completely spooked and unlike himself.
He's scratched my husband and bitten my son (didn't break the skin), he's hiding under our bed and only coming out to eat if we leave food nearby, he's fearful if we make sudden movements and isn't crying to get back out which is very unusual as he's been home 2 full days now and is normally a daily wanderer.
We are very glad to have him back but also very worried that there's something else that's upset him or he's come to some harm while he's been away.
He's been to the vet yesterday who didn't find any physical injury just noted the weight gain (0.5kg since he had his vaccine boosters a month ago).
At the moment we are-
Keeping him and the kitten completely separated. Giving him the bedroom as a safe space where she isn't allowed at all and shutting her in another room on the rare moments he chooses to roam.
Offering gentle affection when he comes out but not approaching or invading his space.
Using feliway diffusers.
Got an airtag and a please do not feed me collar for if/when he does decide he wants out again.
I would really rather keep him home for the foreseeable but he's been an outdoor cat his whole life so I don't know that that's practical if he wants to go back out.
Can any experienced cat owners give me any advice/insight into how we can help him settle back in?