Olishell-
Molasses is good stuff, not so much for your plants, but the soil. Thats high energy food for those microbeasties living in your soil. Marijuana plants are big eaters, so the more those microbeastiest are eating/farting/crapping in your soil the better. They luv the stuff. So no worries with the molasses, i dont know about half cup per gallon, seems a bit much, but i never experminted with that much, but i use 1 tblspoon per gallon to start (beginning of flowering) then up the dose to 2 tblspoons the 3rd / 4th week of flowering until they finnish. (once every 8 days)
Good luck-
Treemansbuds