big bully

Wheels--1 1/2 year old male, not fixed (there is NO ONE in the area that does it, so that's out of the question, sorry).
He used to be with his brother Hollywood, but Hollywood passed away due to myco. So I put him in with Lamont and Phil, but Lamont horded all the food and beat up Phil (who was coming down with myco). I gave Lamont to a friend. So it was just Wheels and Phil, they got along great, but Phil passed away.
It was before I started The Grotto, and I had 3 girls and didn't want to keep any boys anymore, but didn't want Wheels to be alone, so I gave him to a friend. But my friend had a lot of trouble with Wheels and his rat, who were actually littler mates. They couldn't sit on the bed without attacking each other. So my friend gave him back.
Today I tried to introduce Wheels with my rescue boy Milton. In less than 3 minutes Wheels had attacked Milton (who seems very passive).

Should I just let Wheels live out his days alone, or keep trying until MAYBE he finds another rat he likes?