Woah, I'm kind of worried about C, especially since he doesn't seem to necessarily understand that the reality within his relationship is not how most relationships work. Yes, Alec is very lucky to have you, but not because it's some magical, beautiful ideal simply that you're not insane! That's actually pretty standard, whereas the level of control that you're saying C's gf takes over him seems really creepy and unhealthy outside of a context of negotiated, mutually desired D/s.
Maybe Alec could share some literature with him about emotional abuse and talk to him more about what healthy relationships look like?
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.