tl;dr I want to move and take a cat along, how to do it the optimal way given the described situation?
About 3 to 4 years ago, a stray cat moved in with me. His background is cleared, he rejected to move with his former owners over a short distance. I got his passport, so I know he is at least ten years old (first vaccination in a shelter, might be older).
I always accepted his will to be outside the most of the day, and there were months when I barely saw him at all in summer, but he always returned to me in the winter months and stayed most parts indoors then. Especially now that he gets older and experiences back pain (he is in medical treatment) he tends to sleep a lot and barely leaves for longer than two days in a row (he has multiple secondary homes at fellow students and neighbors; all of those that I know care for him move out this year).
I left it open for neighbors to take over care for him, but since no one volunteered, it seems I am taking him along with me. It would be very risky leaving him behind; most of the direct neighbors that take care are students that live here for short times, and most of them drive home or travel a lot. I only now of one old lady that feeds him and will certainly die in this neighborhood, but she refuses to let him in for sleeping (and her neighbor hates cats, he once let my stray bring to the shelter although he was certainly enjoying his life at that time, and really really fat).
Next month I am going to move to another flat. I am worried now, how to do it. Thew new flat is just 1.5km (1 mile) away, but given that the small town city center is between and a very dangerous street, I doubt that he ever went there. When moving, I can either take him by car or carry him on foot - I am worried that he would try to run home and get hit by a car. I don't know which option is best. When I take him at food, I could go a safe way over a bridge, the hope would be that if he decided to return, he would then go this way, I could just fetch him up again (and if I needed to do this a hundred times). If I carry him by car, chances still are that he would know the direction - the way is very simple and he has already been there before on the direct way - no option to obfuscate the way to confuse him (would probably be an asshole move, anyway?).
The other thing I am not sure how to handle is keeping him inside for a month. He really hates it when I keep him inside, and no matter how long he had to, and how loving he was taken care for (I am not the best at that, but a friend of mine tried after the cat had an surgery - still no good). He meows and cries and shouts and gets really loud - while I need to work and study from home and cannot even stay in another room than him. Not the best situation. The new flat is far bigger than the last, however, so that's a bonus. Plus, I could, as an option, have him visit a neighbor he already knows and lives just some meters away, so his first impression would be that his new neighborhood cares for him and that he would have (the feeling to have, surely not a choice in reality) multiple options, as he is used to.
I am also considering setting up a mobile fence - as he has a bad back, he barely jumps at all, I would guess that he could never jump a meter, he barely makes it on the couch. I did, however, see him climb a low fence of another neighbor one day, so it seems I would need to ensure he cannot climb the fence (nor crouch below it). I guess this is doable with acceptable effort, I thought of setting the fence in angle to the ground so the tips point to the inside, that would make the climbing harder (but also the fence a little shorter), or I could use angles at the tips and span net over it, so he would need to boulder his way out, which I doubt he could. I also figured I would closely watch him the first times I let him out inside the mobile fence (which by the way would be built on an area that is not really within the contract, so I'd need to hope no one cares as no one should be impaired by that - actually far less impaired than by the loud meowing if we kept him inside at all time...
He also partly knows to go on a leash - it's not that I could force him (he's still a cat), but I have already used the leash multiple times to bring him to a vet and to let him have some outdoor walk after a surgery (it went like this: I let him decide where to go and just hindered him from going places where I can't [yeah, he figured he could get away, maybe]. At one point, I stop giving in, and at that time he walks home. As long as I do not pressure too much and no cars or scary men come along, he sometimes also gives in to my wishes to go somewhere specific. So walks on a leash would certainly be an option - what about going out with him the first weeks and showing him outdoor places where he can go and relax and is safe? For example, we could go to some meadow and lay down there and later on go back home.
Another thing we considered was taking the cat to the new flat each evening until we finally moved. Like this, he could get used to his new home. He is okayish with driving, he does not like it since it usually takes him to those vicious pet doctors that steal his blood, or teeth, or bone, but neither does he freak out - he drives loosely and keeps lying down even when I open the car's door. He feels comfortable in new environments, being in new flats is no big deal to him. He does that all the time anyway, whenever some human responds to him meowing at a door - he learned that someone eventually will and so I guess he must have seen half the neighborhoods' flats already, and he certainly had multiple sleeping points over the first years.
However, I am anxious that I screw this up. Any advice which way you would prefer doing the move in this situation?