I've been looking at B's chart off and on for several hours, speculating on what might be involved in his issues. Some thoughts: B's story sounds awfully similar to that of a friend of mine, who is also bipolar and also has had multiple run-ins with the law, including prison time and at least a couple of police brutality incidents. My friend is also very artistic, and a painter. He did a beautiful repaint of a mutual friend's home, although because he's horribly disorganized and doesn't manage finances well, there were lots of issues along the way. He is also an activist. Looking at B's chart, I wonder if he has activist inclinations.
Some chart factors my friend and B have in common: they're both Libras, they both have a sun/Pluto conjunction, and they both have Neptune in Sagittarius. The Neptune and Pluto sign placements are generational-- everyone born in the 1970s or early 80s, except for a few on the cusps, has those placements--but because of the combined meanings of Neptune and Sag, I suspect that there may be a higher rate of bipolar disorder in this generation. (Just a theory, completely untested.)
B's sun isn't closely conjunct Pluto, but since they're in a stellium, I would think they're working together. Pluto being on his MC and in stellium with his sun, and the focal point of a minor grand trine, is a powerhouse. He's not only Neptunian, he's also Plutonian. Having the energies of both Neptune and Pluto so prominent is a lot to handle. I suspect that's why his life seems so out of control and has been so full of extremes. Those are very extreme planets.
I see the artistic builder in his exact sun/Saturn conjunction. Libra is the archetypal artist--artists create beauty and harmony--and Saturn is structure, building.
Here's something else I see, that gives even more weight to Pluto: it squares his nodes, at the north bendings. "At the bendings" is where planets are if they're in square to the nodal axis. A planet at the bendings may be at the north or south bendings. If it comes after the north node and before the south node, if you're following the signs in order from Aries to Pisces, it's at the north bendings. If it's after the south node and before the north node, it's at the south bendings. Planets at the north bendings have an especially strong manifestation in the material world. Their meanings will show up again and again, very strongly, in the life of the native.
From an evolutionary astrology perspective, any planet in square to the nodes, from either position, is something you have to work with to get where your going. Pluto is an important part of B's life journey.
The justice theme could be indicated by his sun and rising signs, and Jupiter on his MC. Traditional astrology associates justice with Sagittarius, Jupiter, and the ninth house. In modern astrology, justice is more often associated with Libra, Venus, and the seventh. If I hadn't heard anything about B's life story, I wouldn't look at his chart and immediately say he has major issues involving justice, but if that's the way it's playing out, the indicators are there.
Does B have any inclination to being an activist? Having been a victim of police brutality, he could be in a great position to use his experience to advocate for change. That could mean pursuing a case against the police, exposing them, rallying activists, joining people who are already working against police brutality, or any or all of those things.
With so many planets clustered around his MC, I imagine he has great potential for leadership. That could be deliberate leadership if he has the inclination to take charge, or it could be the more unwitting kind, like accidentally becoming a symbol for a cause.