Do you think that living with you is the best thing for your son?
If someone asked me that question about my own son, then the honest answer would be 'no'. There might be a part of me that wants to mother him and feed him and clean him and keep him between four walls, but it would drive him nuts in a very short time (and me too), even if it's what he thought he wanted.
Maybe helping yours find his own place soon would be the best way to help him stay on this new path. Why did he leave and go and live under the bridge in the first place? Whatever the reason, has that reason changed or disappeared?
It's great that you think he is on a new path, but maybe that path should be about moving on in a better way. I'm not sure that moving back home is the same as moving on in a better way. I would worry about the effect on you too and the effect on your relationship with SO which you say is a bit fragile at the moment.
Just my thoughts, for what they're worth.
x
