Antimatter Drop

well, I dont know how this happens. Sometimes, even when there is no lag, no matter how many times I shot the ball, its damage is very very very low (less than 100). I am sure I am not talking about the impact damage it inflicts.

After playing with Nova a bit, I've been noticing some weird things regarding her infamous antimatter 8411 0f D00M:

1) Sometimes I get lucky and the ball slows down so I can unload tons of ammo in it. After I dump tons of clips of fully modded Despair, I send it flying and see... 300 dmg pop ups... and nothing died... Same thing happens when I shoot the ball and try to keep it alive for long periods (about 3 mins or so). So, is there like a dmg cap or a time limit for you to blow it up before it gets it's damage wiped?

2) What is the best weapon (yes, I know, big dps... but there's more to it than just dps) that you can use with the orbs?