1) Even if it doesn't fit directly, you could use a hotshoe cable to hook up to it to fix the mount position problem. They also have a shot with a pocket-wizard working with a 580EXII, so I don't think that it would be a problem even directly mounted.

2) The 430EX is certainly less powerful than the 600EX or 580EXII. I've not personally tried it with a softbox of that size, but I know the next 320EX is nowhere even approaching powerful enough for that size softbox unless it is pretty dim. The amount of light you need is always going to be a factor. Your best bet when researching this is to look at the number of stops of light that you lose (should be available from the softbox manufacturer) and compare it with the output power of the flash to see if it is enough for your situation.

UPDATE: It seems that it is difficult to find information on the stops of loss that you get when using any of the Ezybox soft-boxes. The best I could find was a claim on a forum that said that Ezybox claims that they only lose half an EV, which is pretty darn good if true.

3) I have a Manfrotto Nano stand and it is pretty good. The 1052 is going to be even more sturdy. The one thing you will need to do with a softbox in light wind though is to use sand bags. Light stands are not tripods, they spread out quick at the bottom and extend up a long way. They need to be weighted down when they have a big sail on top of them.