Re: Frame Reinforcement Issue
I don't think its going to be worth the trouble to fix your frame. Get a new bicycle and start over. Why your frame is cracking is a mystery. My guess is the steel tubing it's made out of is defective, or the shape of the frame doesn't work well for motorizing, but it's probably the metal.
When you let out the clutch to start the bike, don't stop peddling. See if that helps with the lock up problem. How much do you weigh?