At the level of 4tsp per 5 gallons.....You will have no problems....
Molasses is an OLD school trick......It has it's place, and at times I still add a bit......I prefer AACT teas and Molasses plays a major role in making that. It feeds the bio's and adds some Mg, K and S to the game......It might say unsulfured,,,,,but it still has some in play, just not much ..
As far as Mg leaving a "taste" in weed...sigh, the myths that abound around here....LOL,,,,,cure it better and it won't
Mg and S play an important role IN tric production and THC concentrations.