Update:Update:
The maximum distance from any position to any other position is 14. Here is a list of the distances and the number of points for each distance. This is done from (0,0,0,0), but it holds for any point.
The closest items with 3 0's are (0,0,0,3) and (0,0,0,8), which are 5 moves away.
The closest items with 3 0's and a 1 are (1,0,0,0) and (0,0,1,0), which are 7 moves away.
The furthest item with 3 0's and a 1 is (0,1,0,0) which is 12 moves away.
(0,0,0,1) is 8 moves away (to complete the set).
Update 2:
The question was asked how I knew the 8 ring must move at least once, but not necessarily any of the others. There are two different parts to this.
First, if you never move the 8 ring, moving other rings always causes it to move 2, which means it can only ever be at 1, 3, 5 or 7. So you must move it at least once to get it to an even number.
Second, to never move another ring: I expected this to be true because all the ring sizes are relatively prime to each other (and to the moves, except for the 2-move and 8-ring), so if I move the 8 ring 3080 times, I should go through every permutation. If I move any other ring 1540 times, I'll go through half the permutations (because in that case, the 8 ring only stays on odd numbers). To verify this, I put together a quick spreadsheet to simulate moving each ring +1 3080 times. The spreadsheet showed this to be correct. It also showed that you can get to (0,0,0,0) by moving the 8 ring -1 only 51 times.