The seal in those is metal to metal so if some debris got caught in the seal, if you get some agitation in there with the valve full open it might clear. Or some compressed air? Or shop van in the deck fill? Or add a ball valve inline after that valve?
Different areas of gelcoat age differently in color. If repairing, I have had best results mixing gelcoat/paint for each area separately. If painting, pick the color that you are most pleased with and use that color. Eventually, the whole boat will in the new color and paint.
We always rigged an eye on the aft end of the boom and another at the top of bottom half of the mast with a cable between them with pelican hook on each end to support the boom when the mast was down. Keeps the aft deck clear and makes the whole process simpler and easier, IMHO.