Questions About Damage Calculation - Timing and Gain Damage

Hiya!

1) Currently, I'm using a crossbow on my 1st weapon set.
2) I'm also using a (caster) staff in my 2nd weapon set.
3) I use grenades (among other skills) with my crossbow.
4) The crossbow has "Gain 25% of damage as extra physical damage".

Imagine I fire grenades, then swap to my staff to cast something, and then the grenades explode while I have the staff equipped.

A) Do the grenade explosions still benefit from the Gain damage mod on my crossbow?
B) If I had a +Attack Skill mod on the crossbow, do the grenade explosions still benefit from that?
C) Do the grenade explosions still benefit from passive nodes like "12% increased crossbow damage), since I have a staff equipped while the explosions go off?
D) Is there anything else I should consider?

Thank you very much!