Some PVE questions for Void Titan

[Frietbal]

I joined the game to do some PVP and that was cool, but now I wanna do Gambit. As it goes, I find my PVE dmg is lacking and holding the team down.

Because there is still some PvP going on, I would like to keep Bastion as Aspect, and also Bulwark - and this is part of the problem, going without Controlled Demolition.

However, the way I see it, I can take take volatile rounds on grenade kills (echo of instability) and explosion on fatal void dmg (echo of expulsion) to reach this same effect.
Only downside ofcourse, is that I need to get a grenade kill going to reach this same effect.

Is this wrong or right?

Bonus Question: does mods like glaive ammo finder work in Gambit?

Bonus Question 2: I have visited ADA-1 almost every day since I started playing, thats 2 months now, and she hasnt sold any 'Melee wellmaker' Mod yet. Is it so that she can not sell it?