I would call Disney Resort reservations and have any requests added now. I don't think that it is too late. AFAIK, rooms aren't typically assigned this far out. (unless something has changed recently)
I'm not sure why you want to uncheck high floor at BLT? If it isn't something that you want to request, then, yes, I would uncheck it now.
It doesn't hurt to sort out your requests and call as quickly as possible though.
Good luck!