3 points.
1) The deeds that have effects if the shot misses should have a save of some sort. on targeting, either give the creatures that you hit a save verses the side effects OR make this a standard/round action and let them get the effect without requiring a save. for the arms, give them either a Reflex save or target CMD for purposes of disarming/give them a bonus to the Disarm attempt.
2) Dont give people certain deeds for free. Let them pick the deeds they want for their character, similar to the Magus' Magus Arcana ability.
3) Stunning Shot: you should still be able to do x4 damage on the critical and get the stun. you are 19th level. at this point, stun isnt that big of a deal. especially since it takes some feats to get the weapons crit range lowered, and then its still not as good. at least if you have to give up the crit damage stun them for a number of rounds. that seems more fair. if you do this option, give the creature a saving throw.