True. Most contracts will have a severability clause in the end of the contract which will effectively make each part of the contract stand on it's own. I am not sure if contracts without this clause are assumed severable by law like how copyright is granted after a piece of work is created but you have a stronger case if you actually put a copyright symbol on the work.

Technically, that depends on the individual judge's ruling, but either way, the relevant result - the ability to re-sell DLC - remains. Which (in my opinion) is a good thing (if we can get there).