Ugh.
I almost had the same problem a few times.
The best thing to do in that situation is to either A) Look for a teleporter, or B) Look for a phase device and use it right next to the offending wall.
Option B caused me to reappear inside of a monster, which immeadiately gibbed. (Heh heh heh) But this should really be a last resort because you could end up in the middle of 5-6 Sergeants who are all reloaded and ready to fire.
Sergeants+AoB-Escape Route= No fun
As for the trying to attack a barrel with you own hands... I was twice forced to push a barrel into a pool of acid, which blew up in my face, and gave me a "My, that was stupid." message. Then I was forced to walk across the acid.
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Damn you, Kornel. Damn you.
I don't know if Imps can open doors, but humans can.
Another option to solve this problem completely is to remove all barrels from AoB mode. :)
You don't know how many times I've died because some shotty slinging bastard missed me but managed to do max damage to the barrel I just happened to be next to. Or the time I fled a room and pressed up against a wall, which promptly exploded because the shotty slinger took a potshot at an imp, and hit a barrel. After surviving the initial damage, I am now standing in the open with two imps, a vanilla former human, and two shotties ready to fire.
Of course, since Barrels=Evil, Kornel=Evil, and Evil=Evil; Kornel=Barrels. God dammit.
*EDIT!: My awesome ASCII piece of ASCII awesomeness is now complete!!