1) Yes,
2) I don't think so,
3) and Yes, they should
It's not too hard to test the 2nd one. Summon your minion and let they attack you, say, 10 times, or 20. You can get a rough idea what their crit chance is. Then compare the damage of a normal hit and that of a crit, see what the multiplier is. You can cast Enrage on the minion to ensure they will crit.
Your minions have their own Wits score and skill ranks, so I believe their crit chance is what their Wits gives them, and without any rank in Scoundrel, they shouldn't have a crit multiplier bonus, either. You can right-click then examine them and see for yourself. My Incarnate and Bone Widow both have 16 Wits so I think their crit chance is 6%.
Go ahead and cast Peace of Mind on them, then examine them. Their damage does go up thanks to the stat bonuses, so I'd say they also get the extra crit chance from Wits.
EDIT: I have Sebille cast Bone Widow and its crit multiplier is at the default 150%. So no, they don't get any crit multiplier bonus from you.
Last edited by Try2Handing; 27/10/17 03:09 AM.