1) 6 months is a rough average. Some have reported as low as 2 months, some are still taking more than a year. Reservists tend to get slowed down in this process due to paperwork issues. 2 years isn't unheard of.
2) You need to define success. Fit or unfit? Disability retirement? Some view severance pay as their goal. I think the success percentage can be pretty dismal for reservists, as their paperwork about what happened during active service tends to be FUBAR. If paperwork is straight the results tend to be pretty fair IMO.
3) If your unfit disability ratings are below 30%, yes.
4) Yes and maybe. If you are allowed to continue drilling, yes. I cannot answer as far as if they calculate good time if you are getting INCAP pay or something.
5) You will file a VA claim for all service connected conditions and receive a VA rating proposal for them all. If found unfit for continued service for any of those conditions they will become part of your DoD rating. There is a possibility that it is a non-service connected condition that is making you unfit and not any of the service connected conditions, in which case they cannot offer compensation.
6) Compensation is only offered for military service connected conditions. This is a fairly broad standard however, much broader than military related. It doesn't necessarily mean your service caused the condition necessarily. Its more accurate to say the condition had an onset during active military service or was aggravated by active military service. It may be possible to connect one condition to military service and then connect a secondary condition to the first. I.e. service connect hypertension and then secondary connect a heart problem to that. As a reservists, LOD determinations can become crucially important and incredibly difficult to fix.