In order,
1) Identification is not too easy to start with, but after using one you do get to recognise stuff much easier, it's all about experience, I can work most things out in shooting range no problem.
2)no
3)standard picatinny
4) I use a battery pack esp5, never managed to run it flat over 2 nights of constant use.
5) yes, no problems so far after several drenchings.
6) depends on budget, I use a pulsar xq50lrf, for more money I hear the ward is even better, but it comes in over 4K. More than happy with what the pulsar does for me.
7) not that I know, we