Kind of sounds like you need to work on your weak-arm dexterity and strength.

Left handed I work the thumb controlled knife blades on the Leatherman Wave by gripping the blade and swinging the handle, or using the index finger instead of the thumb. Using my thigh. easier if I sit or squat, I can get the pliers open and get the various blades out.

Lighters still work as long as I have a thumb.

When I was younger I dislocated my right thumb and banged up the hand. It was essentially unusable for weeks. Having time on my hand I made a protracted effort to work on weak-hand strategies.

The first time it took me about an hour to tie my boots and the knots failed after a couple of steps. My left hand cramped up and I felt so frustrated. I walked around for a few hours with my boots untied and was quite short with the person who pointed my boots were untied.

After a while I gave tying by boot another try. And another try. After working on it off and on for a day I got it done well enough.

I came up with a double overhand to start as it tightens up better pulling one leg at a time after an initial weak tightening by spreading the hand using both thumb-forefinger and little-ring fingers to grip each side. Then a single loop double wrapped around the other string, a weak spread for initial tightening and working both ends one at a time.

I could get a strong grip for opening jars by sitting on my rump and trapping the jar between the soles of my feet. In some societies its a traditional method for holding items to be worked on. Pulls a lot of strange stuff working that way, expect to be sore, but it works.

By the time I could begin to use my other hand a little I was pretty self-sufficient. Even though it looked like a four-year old's scrawl I could even write a bit with my left hand.

I'm in no way exceptional. Keep working on it and I think everybody can get along pretty well using their weak hand. Once learned it comes back quickly with practice.