Wave sailing issues

I think that it is hard to tell from that video alone (it looks like you are just free-sailing and not trying to head upwind) but I'l give it ago:
1) Back leg should (or can be) straighter, with the heal pointing forwards and you body weight over a slightly bent front-leg, hanging down on the boom in order to increase the mast-foot pressure downwards. On a wave board you cannot use merely the fin (or fins) but instead you use the rocker of the windward rail to head upwind. So you need to dig-in the windward rail at around the mast-foot, in order to head upwind.
2) Sounds more like a technique issue. Try dropping-in with the board angled more downwind, or start the wave ride by doing a snappy backside turn off the lip. You also need to use the rocker line of the board rail in order to turn without loosing speed. You cannot only use the rear rail that has very little rocker in a free-wave board. So here too, it is about digging in the rail where it has curvature/rocker, i.e. around the midsection of the board (by the mast-foot position). So pressure on the toes of your front foot and hang down (elbows pointing downwards) on the boom in order to increase the mast-foot pressure. A lower boom and/or mast-foot further forward helps here.

Is your sail material contacting/draping over the boom ? (it looks like that in the video). If it is, this could be taking away your pointing ability, as doing this makes the sail go back handed. This makes it harder to point.