If it had been up to me, his fate would determined how strong Orlais's Grey Wardens were at Adamant Fortress, as his research would've added Power of Blood abilities to them in three tiers: simple skills like what the Hero of Ferelden had if Avernus died, a few extra talents/spells if he continued his research ethically, and everything being at least twice as powerful if he continued without restrictions. (Hoping we see this in a Grey Warden Civil War campaign with Avernus's Acylotes as a faction.)
About the robes, however. If you were going directly as a Blood Mage, the robes are one of the few objects directly related to improving blood magic as a whole, so I'm guessing yes on that account. I've never played as a Blood Mage, so I don't exactly know how it works.