RTV can't prevent an elbow from warping. I've seen people use a little, a lot and still had problems. The biggest and best things I've found to work are in this thread.

Clean the holes
Lube the holes
Ensure elbows don't have pressure on them

using RTV just means when you swap the next elbow..you need to try and clean that extra crap out.

Aluminum elbow isn't going to provide any better seal (same o-rings), it will..not become a 45* angle though.