Well 1 and 2 are different questions:
Do we proc only on enemy hit? Or is there also a chance of proccing if we shoot a wall? (relevant for gas fe.).
3 makes sense, and allows for some nice builds i guess, but its not being adressed in the post nor stated somewhere else
4 is not said in the post either, as you said yourself
Further there is a 5th question: Does the % apply to all procs seperated? (would make a lot of sense)
So i guess the questions are still valid as neither this post nor the one in Design Council gives a answer to them :/