I miss the days of Candy Corn Acres -- and actual Halloween décor in DCA! There was a Halloween party back then -- the party actually predates the Halloween Time "season" -- but it was held in DCA, not in
Disneyland. Needless to say, the tickets were much cheaper than they are now!
There are still pumpkins on Main Street, so that has not changed.
The way I see it, Christmas is too huge of a holiday for retailers to wait until Halloween or after to put out merchandise. If Halloween things can begin appearing in LATE JUNE (that's when the Three MuskeFEARS bars were spotted in Walgreens), then certainly Christmas things in September (or late August) should be expected. If Valentine's Day things begin appearing in late October, that could be a bit much -- but they appear in late December!
You can view the fireworks from other locations (near IASW, for example), but the details and specific effects (like the sphere/crystal ball thing) and Zero might be better seen on Main Street or at the Hub (around the Partners statue). When I saw Halloween Screams and was standing way down towards the end of Main Street, near Town Square, on one occasion, I couldn't even really see Zero that well, and I could barely see the sphere. The closer to the Hub I was in a subsequent year, the more I could see of the effects.
I think I'd probably go with Wednesday for Disneyland Forever. I think that day would be good.