Is silver worth the effort? Probably. Better to have it than not to, but ask yourself whether or not your flying pattern next year will be of any note -- even if you don't get upgraded, you'll have a better shot at bulkhead seats, etc.

As for which routings yield the best chances of upgrades and minimal use of ERJs/CRJs, well, I'd worry about the RJ problem before upgrade %. You can select your flights and know, well in advance, whether or not the plane is an RJ. Obviously, if your plane is an RJ, you won't have a FC seat (ARJs notwithstanding).