Shavas-- First, you're running great for mid-40s! Very impressive, and it must be gratifying for you. Smoove and others have given great advice. I will add my confidence that sub-2:40 is doable by May. I would suggest, though, that you choose a marathon that's not TOO much of a net downhill course. At least not more downhill than Boston; after this much training and effort, you'll want an honest PR.
By the way, my own progression was 2:47 (warm day, hilly loop), 2:45 (flat point-to-point and 25 mph headwind), 2:40 (hilly point-to-point with slight elevation loss - less than Boston). All three were autumn 1982. Dunno how much was actual "improvement" versus more favorable conditions. Hopefully you will enjoy both!
Happy training, and best wishes.