I use 3 gals for flowering...
rule is 1 gallon per foot of plant height unless you are tying them down very hard.
Molasses does increase resin production. It's almost pure carbon, and the aromatic resins are hydrocarbons. Like you can make a bigger spaceship if you use more Legos, right? Also CO2 is going to give you more yield but you need to get the rest of your grow dialed in first.
If you're just starting out, all you need to worry about is really taking good care of your plants. That White Rhino is going to be plenty resiny.