I have been playing in a Blacksburg, VA Dead band called The Kind since 1986 - started when I was 20. I've been through a buhzillion gear/pa changes over the years and had almost every PA issue you can think of. Sounds to me like your amp is fine maybe even too much for a club gig. I have a Twin that I use on occasion. Love the tone but to get it to where there is enough voltage running through the tubes to get a good tone is often too loud for a club gig. I usually go to my Boogie Mark IV set at the "tweed" setting. I believe it is only running at 25 watts. I can crank it up and get the tone I want without killing the room or my bandmates. We did the amp-less thing for a while and a couple of us still do. I wasn't really happy with the clean tones and I also use a talk box which requires power from an amp. It is a lot easier to control the mix if no one is generating volume of their own. Volume creep isn't as big of an issue - when you have to ask to be turned up you do that a lot less than walking over to the volume knob
- I used a Lexicon MPX G2 as my direct rig - had some really great sounds also messed with a boogie tube preamp though never really found the tone I was looking for and went back to my amps.
As to your drummer issue - really with all volume level band issues it's about controlling your hands and being aware of everything going on not just your own world. If he's too loud he needs to play softer it's really that simple. Keeping issues simple is my motto - there is a great story of John Coltrane talking to Miles Davis - he was telling Miles that when he gets into a solo he sometimes doesn't know how to stop. Miles responded, "it's easy, take the horn out of your mouth." This was a joke of course, but if you start with a simple solution, even if getting there is long and arduous, you are much better off. I say this as one who has learned this the hard way. Our drummer went to using Hot Rods (sticks that are a bunch of small dowel rods strapped together). Our current drummer uses nice Roland electronic kit and that works well though pretty pricey. I agree with Harvestwind - practice playing softly in rehearsal. Being in control of your dynamic level is vital. I love to play loud, sometimes really loud but if everything is at that level you lose the impact of it and it becomes noise. Really loud works only if there is also really soft and everything in between.
My theory with PA is - keep it simple. A good mic into a good mixer into good speakers doesn't need a lot of signal processing. I have a Yamaha 01V96 digital mixer, decent Crest Amps, Mackie mains, and JBL monitors. We use AT 4055 mics (these are large diaphragm condenser mics) and almost no EQ. A little reverb and delay in the vocals but not much. If there is a frequency in the room causing problems we'll do our best to notch it out or boost something that is lacking but really not much. We mic all the instruments for the front of house and all ampless instruments are in the monitors along with balancing out the amped instruments as needed. One mistake we made over the years and have since corrected is using monitors to hear yourself. You need to be able to hear your vocals but monitors should be a tool for listening to each other so you can respond. We put vocals in an even mix in everyone's monitor. If all you do is listen to yourself and use your band just to keep you in time there is no interaction which is what Dead music is all about to me. I have also found that placing your monitors in the right place for the mic goes a long way towards solving feedback problems. Cardioid pattern mics work best with the monitor directly in front of the mic. Super cardioid mics work best off to the side a bit due to the pick up pattern of the mic. I also play in a bluegrass band called Crossties and we my PA but only 2 mics for the whole band one for vocals and one for instruments (large diaphragm studio mics). We stand far enough away that we are somewhat balanced in the mix and when someone solos they step up closer. My gypsy jazz band (Scott Fore and his Hillbilly Hotclub) uses no PA. We use Scherlter acoustic instrument amps to carry the room (large venues we mic the instruments and use a PA). Find the right solution for your band, other's solutions don't necessarily work. There is some good advice in this thread, take it and make it your own!
http://www.youtube.com/watch?v=5Xbn9x-Ctl8
http://www.youtube.com/watch?v=4uv9IEWH2Ho
http://www.youtube.com/watch?v=hE-1BP6hgp8
http://www.youtube.com/watch?v=0wOlTQjMakM
http://www.youtube.com/watch?v=NHgZ6kfaCZM
