Well, i use impact wrenches all day at work, and I can still draw/paint okay. I sure hope nothing happens to prevent me from doing that
Anyway, if the bolt doesn't come off, the impact will jarr, but it's not uncontrollable. The pistol grip on impacts is designed so you can keep them under control. All you'll feel is a violent vibration, but it does not move too much.
I guess it's something you just gotta do.
And if the bolt won't come off ... Beef up the power or use a large breaker bar. When I did my struts all I used was a breaker bar and a ratchet that was placed against the ground.
As for the size of the bolts, I don't remember. I think 21, 22 mm? Not sure. But be sure to use impact sockets with an impact wrench, it's not fun getting chunks of Craftsman socket imbedded in the soft pink bits.
As for the stoppers ... No idea. I have never really looked for them but i'm pretty sure universal ones ... if they exist... will work.
Have fun!