"Who will determine if Apple’s rounded icon style is worth 1% of the Samsung Galaxy profits, or 10%, or 99%?"
This bit seems pretty simple to me. Say a phone has 50 patents applied to it's design, then one of those patents would be worth 2% of the profits. Therefore, if only one patent is infringed, then 2% of the profits would need to be paid.
There would need to be another rule in place that stops patents being combined. I.e. You shouldn't be allowed to mix the 'app icon grid' patent with the 'bezel' patent (which they don't currently do anyway)
All in all, you wouldn't get companies patenting absolutely everything in their product because if someone infringes on it, the percentage payout would be a lesser amount. Companies would only patent the elements of their design that they feel are the best solutions!