1) It should be a matter of policy that anyone making false/unprovable accusations against another member be banned for trolling.
I would say that this should happen for outright stupid ratings (of which there are plenty under untrusted feedback). Good luck convincing theymos to change this though. 
2) The ridiculous "trust" system allows anyone to troll anyone, often with fake + and - comments.
Yup. The trust ratings don't even have a sane length limit. I have suggested that it be added at least on one occasion; I'm not sure whether something has been done in regards to that.3) Nobody should be able to "rate" another user without having done business with them directly..
No. This is a trust/reputation system, not a 'trade system'.