Training of each delt separately ?

[Honkey_Kong]

I have 2 problems :

1.right arm stronger than left arm
2. Rear delts unbalanced with lateral delts.

It is unbalanced because I rarely Train the rear delt... now I always start with the rear delt and my right arm is stronger than my left arm. I improved my rear delts and the right arm is about to catch up.

After my boxing work out, I have just the required energy to work 4 x 10 reps of one deltoid...

I don't know how intense your boxing workout is, but maybe do your lifting before you do your boxing? Maybe an energy drink or a stim preworkout is something you need?

You ever think about adding seated shoulder presses in to your workout?