The final part, its managing all the projectiles, the red rings and his melee, I got close just on a run now, Shockstream does some good damage
Hmm. I just watched a refresher vid (can share if you want it) and can see how it would get tricky as he's jumping quite a bit. I'd say be patient and focus on avoiding the rings and melee attacks, wait for an opening to start doing damage again. You're not in this to finish quickly, so don't rush it.
You can also melee to give i-frames if you time it right, in case you just dodged or jumped and can't avoid an incoming ring.
As a general rule as I've said before, stack protection. You can take a lot of hits when your protection is high.
For a weapon I love the hallowseeker, though it can be pretty OP. I would go with that if you can find one, even if it's "lower level," the perks make up for it. I won't list them here but you can view what they do in the inventory screen when you pick one up.
These boss fights are all about not panicking when a flood of orbs and shit is coming your way. Continuing to fire makes it fairly easy to just move out of the way of most of it and other stuff you can just run to one side or the other.