I only fish 3/0 if I have to. 95% of the time you can use size 2-2/0 and you'll be fine
I know a guy that ties all of his SW flies on 1/0, no exception
I fish a normal freshwater floating line much of the time myself but most people go with the intermediate. If you're going to cast and strip that's what will work best in most situations.
I like my floating line for dead drifting current and mending over breakers.
I normally fish an 8wt rod too, but rarely with a 8wt line. One of my rods works best with 9wt lines and the other likes 11s... really. It's the line that casts the fly
When it's really windy, like up over 25 knots, I'll switch to a 10wt rod, 12wt line.
I watch Craig's list alot and I see many good saltwater combos for sale
The recent drop in the striper population has shied away all but the hardcore fly anglers