U clearly don't know anything about DB, reason why he never went ssj3 was because HE knew it was a massive power drain, and Vegeta's fighting style is overwhelming opponents with powerful ki blasts. That's why he decided to master ssj3 by becoming an ascended ssj2 by becoming majin. By going ssj3 he would deplete his kibin less than 30 min. Goku stated this when he fought against buu, he even told this gotten and trunks AND then again during the tournament of power he told this to Caulifla. Vegeta told Cabba to not use that form since it would mess up his power reserves since the transformation is complicated at first and even harder to master.

The ending was lacking, he said he would reveal Dekus dad and didn't, hopefully he does a spinoff chapters where they tie loose ends and explain the relationships of everyone. And give us that happy ending

He dies, before his duel the shaman made a reference to the sands of time running out, during the fight you see the sand from his hands run out and what was left blew away, he dead, his whole world died with Julia. He knew, he wasn't coming back. People that say it's left ambiguous are like those people that claimed that Aeris could be saved if you did x thing on FF 7.