Remus
We both know Dumbledore doesn't always tell us everything, or even have our best interests at heart, but if you trust Snape Severus, I will too. Besides, he hasn't been a complete arse lately, I don't think he'd poison you purposefully, and he's too much of a perfectionist to do it accidentally.
We've faced situations with worse odds, and at least this isn't life or death.
Yeah. I don't really see how it can be fixed at this point. They're both living in the past and refusing to see the other's perspective. You've gotten to know Regulus though, do you think there's any compromise to be found for them, or is he going to expect Sirius to shoulder all of the blame for the state of their relationship? That's the impression I'm getting, but it's biased through Sirius' eyes.
Or maybe we just stay out of it altogether and let them figure it out.