Hi Christian,
Small venues are, indeed, challenging to photograph in. One has to combat crowds (and huge pits in some of the shows that I go to), ugly monochromatic lights (reds are possibly the worst for photographers!) and all the mics, stands and cabling on stage.
You should find the Sigma 28 or 30/1.4 to be quite useful. I have found the FA 35/2, FA 50/1.4 and FA 77/1.8 to be absolutely indispensable for gig work. In fact, I go with those three lenses and no other. (Of course, the FA 31/1.8 and FA 43/1.9 should be good as well.)
Looking back at my concert pix, I have not shot above f/2.4 and most of my shots are either at f/1.7, 1.8 or 2. Stopping down further can help add some motion blur which can be quite effective in conveying the energy of the show.
B&W conversions can be quite useful in bringing the main subject(s) into focus. It also allows you to burn out the distracting elements in a frame with greater ease than doing it in colour. Pix 2 and 4 could benefit greatly from this, IMO.
Here are some of my photographs from gigs:
1.
Zenfolio | Nikhil Sarma | Noctilucent (K100 + fast lenses)
2.
Zenfolio | Nikhil Sarma | Lestat's, Apr 20, 2007 (K100 + fast lenses)
3.
Zenfolio | Nikhil Sarma | Scenes from a Cafe (Mostly from my DL days)