It's a Kappa antagonist, not a partial agonist. It's fairly good at blocking Salvia's effects. Not a ton. The drugs listed, however, are not ones for which I'm unaware of any interactions.
At .2 to .8mg to per day? This isn't Suboxone maintenance, apparently, is it? Cutting a 2mg strip into quarters (.5mg) is annoying. cutting that in half (or even less than that, to get .2 even) would leave you almost nothing.
Doing that with the pills would be really tough to measure accurately.
I noticed with salvia that the effects were more or less completely blocked until I took exceptionally high doses. huge doses, really. >3mg smoked. And then it was severely muted. I didn't get that sweaty feeling though- but I didn't get much more than the gravity if my memory serves me.
buprenorphine does not change the effects of cannabis. I never noticed anything at all, though while on it I rarely smoked (and now I never do). I'd be extremely careful about combining it with ketamine and GHB, but done carefully the former should be fine. I wouldn't do the latter at all personally, but I'm fond of breathing. The others should be completely fine. Amphetamine itself is not effected, and mushrooms produced normal effects, so I would assume that MDMA would as well, but that's not something I ever tried.