And again, as far as the hotspots go, you can really put them anywhere, they don't need to be near plate boundaries.
2. I think I lost my train of thought briefly when I was taking about your plates and just got focused on what direction they were going. I was comparing the three sets because the pairs were moving in unison but, as you say, there weren't any mountains between two of the pairs, as there right oughtn't to have been. So, Kudos for you. My bad for the confusion. /smack
B, C & H coming together should develop a very high mountain range. However, since all you're dealing with here is continental crust (not as dense or high in water content as oceanic crust), there probably won't be a lot of volcanos, just really really huge mountains (like the Himalayas). If volcanos are a must-have you could stick a deep inland sea in there somewhere next to where the mountains are forming, it being the last remnant of some ancient ocean soon to disappear forever (like the Mediterranean).