I only used mine on my driveway. Since there are two jets, the pressure on each is less than on a single jet. I think it woulld be fine for a composite deck.but I don't know for sure.
No but my guess is that it would destroy your shingles
I uses a 4000 psi and it worked great
No you cannot change the nozzles. I suppose you can purchase different nozzles of the same size but you can just move it over to cover an area much easier. It handles like a vacuum cleaner so you just move it rather than change the nozzles.
Just hook up your water hose and the machine will pull in the gpm it needs.
no, i recommend the Ridged 18inch surface cleaner,
Nope, what you see in the photo is what you get.