Sounds like you’re making progress in the right direction.

I had some success in freeing up a couple stuck injectors by turning them upside down, clamping a 6” length of hose to the pintel end of the injector, filling the hose with carb cleaner and letting it soak backwards through the injector for a day. Then I made sure the hose was full and rigged an air compressor hose to it so that I could apply about 30 psi to it while hitting the injector with electrical current - tap, tap, tap with the electrical charge to simulate a running engine. This will back-flush the filter inside the injector. Don’t clamp the hose to the pintel cap as it might blow off when pressurized. Clamp it just above the cap. At the time I thought the injectors normally operated on a 12v signal so I used a jump lead from the car battery. I was subsequently informed that the injectors normally open via a 5v signal so I guess I was lucky that I didn’t fry any injectors. But hey, it worked. I captured the fluid that flushed through the injectors and saw some sediment in it.

I chose to remove the Pinter caps during the cleaning process as I didn’t want to force any crud, that might be residing within the cap, back through the injector. Also you might find that 3v isn’t enough juice to unfreeze the pintel. I wouldn’t have any hesitation applying 6v.