Not a bad effort at all for a first time. Nice job.
I shoot a lot of theatrical productions. Best is when the producer/director arranges for me to shoot at a dress rehearsal. I can move around freely for best angles and not worry about being in someone's way when I stand up to shoot from audience seating. If that is not possible, I do what you did and get the best shots I can during the actual performance.
That said, I'd encourage you to get some longer glass if the budget allows. That will allow you to get in tighter without actually getting too close to the stage. I'd also encourage you to not be afraid of higher ISOs. Many of my stage shots are made at ISO 6400 or even ISO 8000. With the speed up that much, you can shoot at a smaller aperture, say f/5.6 or higher. That way you can still shoot at higher shutter speeds and deeper DOF, freezing motion better and not losing sharpness on actors behind your immediate focus plane. You will probably have to run shots at such high ISO through noise reduction software (I use Topaz Denoise 5) but that is the cost of doing business in theater lighting. I'd also avoid Tungsten WB as theater lights are much warmer than that. Since they use colored gels on most lights, it is difficult to get it right anyway so I usually just leave WB on Auto and make any needed corrections in post.
Not to highjack your thread, but here are a couple from a recent production on an outdoor stage at night to illustrate. #1 is at ISO 6400 and #2 is at 8000. Posted in low-res as I don't have releases to publish. Please don't rat me out.