....Qs about ArKaNa.
1 - I hadn't given this much thought as I designed the whole of ArKaNa in about 4 hours! I'd say keep a track of every '6' rolled. Use these to increase the trained value at a cost of a number of '6s' equal to the new trained level times 10, with a maximum trained value equal to the natural value times 2. IE. to get a trained value from 2 to 3 costs 30 '6s'.
2-To increase a value from 3 to 5 for a single round costs 9 DP because it costs 4 DP to go from 3 to 4 and an additional 5 DP to go from 4 to 5. AND yes, I'd say that my description is "mangled" for want of a better word. Roll on the next edition!
3- I'm not fussed if characters can't carry that much.
4- A passive difficulty is the same as an oppposing ability except that it represents the "world". And yes, the"world" rolls more dice if the passive difficulty is higher than the character's ability value.
5- You answered this in the first line. "Highest single roll wins a round". If there is no single highest roll then a draw results. It makes a character with a higher ability score to be MORE likely to win because he's rolling more than 1 die BUT he can still roll low on ALL his dice rolls while his single die rolling opponent rolls a 6!
6 - sure. Any house rule is OK here for combining efforts. I have no strong feelings here as I've seen different methods for handling such situations. whatever you feel is best.
7 - i wanted magic to be something erratic, unprovable and potentially VERY advantagise. I imagined something similar to the magic in Neil Gaimen's book "American Gods" were the magic "happins" but is never "seen" to happin.