I also use a mineral spirits soak to clean my chains. I actually keep a spare in a jar of mineral spirits and swap them out on all 3 of my bikes once a month. For any of my bikes, the chains I've had the worst luck with are KMC, specifically with their cheapass masterlinks not shutting properly. The rest of the chain has been fine, and I've never had one fail (which is amazing, considering my weight), but I change out KMC masterlinks for SRAM Power Links, and I use SRAM chains on my geared bikes.

Good chain breaker: Park Tools
How to judge wear: Chains should measure 12" even at center-to-center of pins. If it's more than 1/16" from the center of a pin for 12" of chain, it needs replaced.
How much corrosion is too much: ANY.