Whether or not it goes turtle depends largely on the angle at which it capsized. If you go over with the spinnaker up, there is a good chance that it will go turtle as you usually turtle because the wind is immediately pushing on the bottom of the trampoline. If you can quickly get someone out on the daggerboard you can usually avoid the turtle.
Getting off the high side of the boat? Swan Dive off the stern (be sure to be unhooked from the trapeze). If you are swinging somewhere between, you can step on the boom but try to do it near one of the ends where it is supported by the mainsheet or the gooseneck. It is weakest in the center of the span between the two.
We DO use our downhaul for gust response in moderate breezes...if you've got just enough wind to trapeze normally, then use the downhaul to manage the power. If you are starting to get the downhaul to the maximum setting frequently, you should set it at an average setting - about 80 to 85% and use the main. If the wind is really high, crank the downhaul on fully and work the mainsheet. If that's not enough, drop the mainsheet traveler down a couple of inches and work the mainsheet. If that's not enough, drop the traveler down a foot and work the mainsheet. If that's not enough, just enjoy the ride, do what you can and hope you don't need to reach!