Various points.
I agree with Cockie's comment #7, the puzzle isn't balanced.
MandyRob, the outer ring is a 4-letter word including a hole, opposite of subtract; then synonym of Robs minus T; then 3-letter sailor inside a source of formic acid (3,3) also including a hole.
I forget who it was, but someone made a very strong argument for 10-7, in that if 13 and 14 hadn't both been the same direction they would surely need to be counted individually.
And like others (I suspect) I don't have all the extra letters. In fact I only have 2F(?), 5C, and 6D. But perhaps it doesn't really matter, or maybe it does if the ring values are to be used as coefficients in the scoring system (which would make sense...in which case what would be the coefficient for the centre circle ?)