I would try to get the back pain under control so that Back Squats can return to your training protocol without any pain. I'm not against only doing Front Squats for a cycle, but I wouldn't drop them forever.
The thing with the Squat/Power Jerk is that you should have really strong legs and you must have the mobility/flexibility for it. It sounds like you have the mobility so make sure your legs are strong enough to handle that movement after the cleaning it. Then again, you're new to the sport and it's going to take a little time to develop some comfort with these movements; that goes with people of all shapes and sizes.
With the Jerk, I would not recommend using a false grip on the bar. Some people find it more comfortable with that grip but I recommend trying to find a comfortable grip with your thumbs around the bar. I hope you're not using that grip with Snatch-related overhead exercises (OHS, Snatch Balance, Snatch Push Press, etc). In that case, definitely bring your thumbs around the bar.