This is what every drummer faces. It's simple in concept, you have to work your weak hand until it can play as good as your strong hand. There's no shortcuts, just a really long road to go down. With no shortcuts.
I've had my own journey getting my left hand equal and it's finally here. I started at least 10 years ago, but it could probably be done in 2 with many hours of focused practice. Me, I'd do them here and there, a few times a month, hence the 10 years. What I did was observed my good hand in detail...which muscles was I using, angle of palms, every detail. I realized I was using a different (worse) technique with my weak hand, which is where my imbalance stemmed from. (the physical not the mental!)
While my playing sounded even enough....I myself didn't feel the same in my weak hand as I did in my strong. I didn't feel I was a balanced machine. So it took me years of focused attention on my left hand, always comparing it to my right hand. Fold in a heaping helping of pain in the form of burning forearm muscles and there's your recipe. Today, when I play, I feel like I have 2 equal hands now.
FWIW, the exercise that really helped my left hand...I do a full on shuffle rhythm with the left hand on the snare. Now add in a really strong backbeat. This is all one handed. That was a killer for me in the beginning years. The spang-a-lang jazz ride pattern is also a good exercise for dexterity and fine control in the weak hand.
I focused on my left hand for so long, that my right hand got a little sloppy by comparison, so I had to bring my right hand up to speed after a while. That's the kind of problem that I'll gladly take. That went really fast, sharpening my strong hand. It only took a few practice sessions.