Does using high temp RTV silicone work to stop oil leak on broken distributor o ring?

Yes if it's done right. the way I've always done it on a Chevrolet 350 is to spread the silicone around the area trying not to push it to close to the inside edges but still make a nice bead about a 1/4 - 1/2 inch tall and then set the distributor into taking care to make sure that you are properly aligned. now then the trick is not to tighten it down until you give it some time to set up. give it a while then torque it down. has worked for me every time. hope this helps you