1. I have had good luck basing my exposure in ISO 1. I assume you are exposing the plates outside in sunlight or bright shade. Remember the plates require UV light to expose.
2. I get best results pouring the developer on the plate in the same manner as the collodion. You don't need much developer--half a shot glass. I time the developer--15 seconds I think (I'd have to check my notes).
3. Have you viewed your plates against a black background? Just put them on a black cloth and see how they look. Glass plates look thin compared to negatives.