I hope Gremlin pulls through okay. If you live in a state with a cold winter, it might be a good idea to just keep him in through the season. I, personally, think most cats should be indoor only as they can have all sorts of things happen to them on the outside. Now that he’s in his elder years, he may be able to thrive much better if you do. Just give him lots of love and playtime and he most likely will get used to being indoors. Maybe he and Wolfie will become besties! Good luck.
Agree. My cats are indoor only., but I had the decision reinforced a couple of days ago when something took down a full grown deer in front of the house, ate part of it and left the rest for me to deal with.