Trav,
You should be able to answer this from your own first post.
You couldn't get going on the wakeboard, but could on a surfboard. It is the board.
If you search this forum there are many queries about using wakeboards and every one I have read someone has said they are absolute crap to learn on. JayP and Stamp have said why, and I know JayP tried the same thing when he was learning and said it was the worst mistake he made. I have heard of some more advanced riders using certain types, but that is only in dead flat water, and they use them for tricks.
Regarding your comment on the kite falling out of the sky.
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So would shortening the back lines make the kite more likely to stay up at 12 o'clock when you let go of the bar instead of just slowly crashing to one side?
No - inflatables do this by design. Let go of the bar and they fall to one side. They don't auto zenith (go back to 12 o'clock). Some ram foils do this though.
Shortening the back lines will increase the power for a given bar position, but it will also shift the stall point away from you as well. In light winds this means you can get maximum power where you normally have the bar in cruising mode, but pulling the bar all the way in may stall the kite. I do not recommend this if you are learning as it will likely give you more grief than benefit. Fix the board issue first and try again in a bit more wind, it will help more.