I was looking for a plum wine recipe but everything I found was SWEET ugh so I made jam instead,does anyone know why it turns out sweet?
I've heard it explained this way: If you start any wine with too much sugar there will be sugar left over after fermentation ends. It ends because the alcohol level keeps rising and eventually kills the yeast which can only survive in a certain percentile of alcohol. Different types of yeast can survive at different percentiles though but as I recall most give out around 14% or so. ? (Not sure of that number)
The goal should be less sugar but enough to reach an alcohol level that protects the wine from spoiling (over 12 % I believe is needed to protect it). It is important to write down the specific gravity of the juice before adding the sugar and only add enough sugar to reach a final specific gravity needed to reach which percentile alcohol you want in the finished wine. Then if you want it a little sweeter you can always add a little sugar syrup before bottling (just make sure the yeast don't wake up again and start fermenting if the alcohol level wasn't high enough to kill them off.)
Also there is a difference in recipes between British and American- your gallon is larger so if I try your recipe in my smaller US gallon it ends up too sweet.

why we couldn't stay synchronized to the European system is beyond me and still not metric!