As long as theres no sugar or syrup or coloring, and no preservatives, it should be good. It may contain diacetyl, which is no good for the long run but i vape it anyway lol. Diacetyl is a buttery rich taste; think microwave popcorn and modelo negra. If it has that same buttery richness there it has diacetyl.
TFA Tobacco? No clue never used it. Id start a small bottle with 7% custard and 2.5% tobacco, and another small bottle at 5% tobacco by itself. Keep trying the tobacco custard mux by itself and leave the tobacco alone and try it in 2 weeks. You should be able to really dial in on what the full flavor is supposed to be like. From there adjust up or most likely down til you get it right. What are you going for? A rich full custard with bold tobacco or a hint of tobacco? Bold tobacco with a hint or richness?
tbh a Graham tobacco custard was what i got into DIY for a couple years ago.... I eventually gave up because it was too hard to get it exactly how i envisioned it. My favorite tobacco ended up being RY4 Super Concentrated by Vapingzone