Give your peel a quick back on forth while its still sitting on the counter before you head out to the grill. If it doesn't slide when its flat from a quick jerk, it's going to dump all over the place when you have it at a slight angle putting it on the grill. I have a friend that will lift one edge of the crust and give it a good blow under between the peel and the dough if it looks like its stuck. It actually works fairly well. I'm not sure if others have noticed this technique when he's done it. It doesn't bother me, but I'm sure some people won't be fond of the idea of possible spittle.
I've also never used a metal peel for putting pizza on the grill. I'm guessing the temperature of it or some other property of a metal peel make pizza more likely to stick thus the common use of wooden peels.
I think 3-4 binder clips around the bottom kettle might give you more airflow when you put the lid on to give you higher heat and possibly some flame that you need to get the top of the pizza cooked nice. I'd warm up your stone with the lid off for 10-15 minutes then another 10 or so with the lid on to make sure its hot enough. Until I realized you are using your Summit!!!!! How hot did you have it running? I'd shoot for 600 degrees, and put the stone on as soon as you get your coals situated so it warms as the rest of the grill is getting up towards the smelting portion of your thermo!
I'm wondering what kind of results you will have with bottom vent wide open and the top one wide flipping open? Do you think you would have enough flow to get some flames if you added hardwood? If not, use wood sparingly....a little smoke from smoldering wood chunks goes a long way with pizza crust. Flaming wood is an entirely different story, the more the better.