I've got a theory now on my "slight metallic" flavor. I have one cheaper stockpot as a backup; most often used for bottling, but might have finished in it once or twice too, that i got at a yard sale and has a worn paper label on it saying "stainless steel" but the handle rivets are very pitted. I think these rivets may not be SS. I won't use it again.
For my density, I think at boiling I rushed too much so temp didn't stabilize on the murphy cup. When I double checked it near room temp before the contest, I used my smaller cup that barely fits the hydrometer. Between being more viscous (cold) combined with some potential capillary action on the hydrometer, I think I got a false reading there.
For my slight sour sap taste, well, I guess I can't necessarily boil only on weekends and Wednesdays! Will have to keep up better! I'm using the last jar of this batch now and it still tastes pretty good but I think I see what they mean. The sap must have fermented just slightly before boiling.