Larry give you some excellent hints. But there is another good way to overcome the bad autofocus system. I use a cam remote from DigiPin (PanRe), with this remote you can program 3 focusplanes. I use it often in dance halls. 1st is front 2nd is middle and 3rd is far. So I can quickly change the focusplane by pressing a button on the remote. This works great! No focus hunting at all, even in low lit environment. And yes I'm also using an external Monitor. I's much better because I'm always have a waveform monitor in the right lower corner on to see the correct aperture setting...
Good luck