273 questions...a few of them

I'm not sure locktite will hold a loose adjust screw. Maybe someone has used it there before and will chime in.
Proper fix is to replace the rocker. Yeah that sux.
The mechanical pricipal used there is interfearence threads. Means the thread per inch and'or thread pitch on the screw doesb't quite match the threads in the rocker.
Since the rocker is ductile iron the wear and looseness you have is in those threads. there isn't anything you can do to those threads but... you can distort its threads a tiny bit. Dont feck with its first couple of starting threads and dont over do the distortion.
Still others have simply staked the screw and rocker together with a keen punch after the lash is set like staking a jet or venturi tube in a carb body. Someone much more experienced might know what method works best.