Need help!
Had gearing problems with my Motolite since I got it. The latest problem was the gears grind when the full suss is unlocked and climbing in a low gear.
Tried everything and have finally decided to change the short shadow rear mech to a long one.
Now I have a new problem.

The chain is popping off the front towards the frame. The limiting screw is in as far as it will go, but still an issue.

Please can anyone suggest anything to get my set up right?? Can I put a longer screw in??? Is the derailler knackered?

Any ideas appreciated.