Should I support my musician boyfriend pursue his dreams while he depends on me financially completely? He has been trying for about 6 years.
No. You should tell him to get a damned job and pursue his music on the side.
It's time to stop trying and start doing. And when he takes on his job, he should take on doing it with excellence.
And then, especially if he hates his job, tell him to double down on his music. Work full time at his job, and work full-time at his music, with the same damned intensity.
Then he'll know if he really wants his music, or just likes calling himself a musician.
And don't let him get away with just practicing. A musician performs. Make sure he's booking at least one gig a week, and giving it his all.
But don't you dare suffer for his art. If he wants to suffer for his art, that's great. You can drive him to his gigs, be his sound engineer if you want, and be his biggest fan, but he's got to take on being the damned artist.