Tips on getting final gravity lower for molasses rum wash?

[Doctor Dunder]

Hello! Asking for some rum wash fermentation advice! My issue is I cant seem to get my final gravity below 1.05, and I feel like I’m leaving a lot of sugar left in the wash! I’ve probably run about a dozen batches tweaking a lot of variables but always seem to end with the same FG.

Here are the specs of my wash. My recipe has been around 1 gallon of molasses, 1 gallon of dunder, 3 gallons of water, and 2 tbs of yeast.

The variables I’ve tweaked are different types of molasses (black strap and feed), different yeast types (distillers and bakers), various levels of dunder, between 0.5 gallons to 1 gallon, and have experimented with different yeast nutrients like Vitamin B or epsom salts. Fermentation times run on the longer side, around 5 to 10 days. I usually try to isolate and change one variable each batch, I've kept good notes, happy to discuss specifics. My original gravity is usually around 1.07 - 1.08, and starting PH is usually around 4.5-5.0. Fermentation temps have been warm (in a garage here in Texas).

I am attempting a pure molasses/dunder wash, and trying to avoid adding any additional sugar if I can help it, as my goal is to achieve high flavor high ester rum.

No matter the variables I tweak I consistently end up with about 1.05 final gravity, usually around just 2.5-3% abv! After a dozen or so batches I think it might be a systematic issue perhaps? Any advice or direction would be greatly appreciated! Thanks!