Lee
Diffs should feel free but not slip. Its as simple as that really boss
Tighten the slipper right up to initially set the diffs as you dont want to feel the slipper slipping and confuse that for the diffs
Slipper is all about the track really. Best to bed the diffs in with a tight slipper to check for "barking" and tightness, then loosen the slipper off till you get a few feet of slip from a standing start.
The other way I have seen it done is to stand on your car and hit the throttle...if it slips its a good start lol
Front and rear driveshafts level is a good start, maybe front shafts slightly (slightly) higher to calm the front down.
Are you running high grip or low grip track? if high grip you can get away with a slightly tighter slipper to get more traction but not so tight that it eventually fecks your diffs up.
As for the more indepth stuff, there are alot of good Kyosho drivers on the forum who'll hook you up a setup id imagine