Answers...
"1) Do I need a y-valve with lockout feature to be "legal" in Gulf of Mexico, Florida, Fla. Keys, over to Bahamas?" It would be a good idea...for several reasons, not the least of which is, it provides the ability to shut of the flow of tank contents to the macerator or manual pump when you need to service it. However, you only a means of locking the seacock on the thru-hull to meet the letter of the law. "2) Will a mascerator empty a holding tank discharge (with dip tube) mounted on top of tank? It should. "3) Any secrets to pulling/pushing new sanitation hoses through bulkheads, etc. like attaching old to new with couplers or wire or fish tape?" Male-male couplers are the only way to make sure the hoses can't come apart if you hit a snag. Use PVC cement to attach the old and new hose to it...cut the ends as smoothly as possible, so that they butt together tightly...you don't want the connection to get hung up on anything, so you want the smoothest unbroken surface possible. After you've pulled the new hose through behind the old hose, cut it off behind the fitting.
