1. The jib track controls the angle of the jib while the jib sheet control the twist. Is that a correct belief?
Not entirely. For the jib you have 4 controls although not everybody considers the luff tension to be a control. Anyway in addition to luff tension, you can and must set :
-1- position of the traveller car
-2- position of the shackle to the clew plate jib
-3- tension in the jib sheet.
All three combine to give you a particular draft, twist profile and angle of attack of the jib. Change one and you'll probably have to change another as well or accept sailing with a sub optimal jib for a while.
Typically you trim and tune the jib for upwind work and take what you get on the reach. On the downwind you are flying your spinnaker and then the jib is pretty unimportant and more often then not the upwind setting with a little less tight sheet is pretty good then.
2. Is it possible for the self tacking jib to back wind the main since it doesn't overlap?
Yes.
The jin CLOTH may not overlap but the flow coming of the jib still does.
3. Where do I put the jib car going upwind? I normally put it around 10cm in from the edge of the track. Is this right? Is the jib car setting something that you guys adjust a lot on an upwind leg of a windward leeward race course?
That is something you must find out for yourself given the brand of your jib and boat. Not much prior experience here yet (Viper + Goodall jib). Personally I don't adjust the jib car position after I leave the beach. I set it is the right ball park on the beach and that is how I'll sail. I certainly won't adjust this setting when switching from upwind to downwind and back as I want the optimal setting for upwind back when passing through the gate. I simply takes to much time to reset car properly and even then you hope you have remembered it right.
Wouter
