IME, being a "very laid back guy" will get you exactly what you don't ask for. Mostly that will be nothing or somebody's left overs.
You're used to putting other's needs before your own and expect others to do the same.
I was exactly the same until I wised up. It took a long while. Too long.
IME, this is a fundamental thinking error. In fact, IME, most people do what is best for themselves to get ahead and will take up "your space" w/o a thought to "what you need". Learning how to not take this stuff personally takes a serious personality "extreme makeover" because it can be so "unnormal" to you. IMO, That's why you get upset when others don't act like you would have acted.
Not being able to control other's behaviors and getting upset about it is the best way to be unhappy all the time and create health problems for yourself. Their actions are not directed at you! I suggest you stop taking them personally.
IMO, it doesn't. I mean, the guy is standing 10 feet from you and all you had to do was speak up. You could have said "I know we discussed a stereo setup in rehearsal but this gig/stage is not the time to test it. Please take it down and we'll test it another time."
IME, not having a wide enough stage pretty much renders his "stereo" effects useless. IME, a better solution is to run him stereo to the P.A. and keep the stage volume reduced.
No, I think you've analyzed it fine, however, IMO, it's that you haven't analyzed how you respond to people when situations like this come up. Seems like you may think speaking up for yourself creates a confrontation and you don't like confronting people. Speaking up for yourself in an articulate, thoughtful, reasonable (possibly humorous) manner is a real skill.
If you respond the same way to all situations when you feel a loss of control, then, IME, it would be very helpful for you to improve your communication skills.
Your "laid back" guy description kinda paints you as a passive guy, not really willing to take a stand, verbally or otherwise, when you feel mistreated in some way.
Especially since you started the band and haven't worked out with your band members about when to show up for a gig. He shows up 2.5 hours early....you say 1 hour is fine.
IMO, the main reason the guitar player is acting like it's his band is that you are not being the leader. You say that he books the gigs, sets up the P.A, brings in more people...sounds like he's more serious than you are. Or maybe he is taking over the "band".
Since your guitar player seems to be a pretty sharp guy, and with him putting his second amp right in the spot where you're supposed to set up tells me that that he's possibly looking for a confrontation from you. He's knows you're passive and may be attempting to create a situation where you will blow up/quit so he can bring in one of his buddies.
I'd schedule a band meeting and get everyone on the same page. Decide on who's the "leader" of the band or is it a democracy?
Here are a few links you may want to check out:
If I only knew then...
Best musical advice
Democracy/dictator?
"Leading" a band
Remember, freedom of speech goes both ways. If others tell you what they think, it's okay for you to speak up as well.
However, if you're unable to be a better communicator and leader, I suspect you'll run into the same problem again with your band members and pretty much in your non-band life as well.
Just curious:
Who owns the P.A.?
Does the guitar player have family?
Is he also the lead singer?
Who else sings?
P.S. sorry for the long answer. Being passive about stuff has screwed up a lot of things in my life. Hope you learn sooner than I did.