Agree, solid foundation. I noticed right away that your hips are not pointing forward and that there is a lot of arch in your back, which I suspect is shortening / undermining your catch, and also impacting your lung capacity. I also noticed that your ski is much too big for you in the cockpit.
A few tips that might be helpful:
• Sit upright, and lean forward from the hips - not the spine. Your chin should be just in front of your groin.
• Keep the foot pressure on your drive leg throughout the entire stroke (from catch to exit until your next catch, then unwind). Don't release the foot pressure until the opposite catch has been made the blade is fully submerged. This will feel chunky at first, but you'll notice a lot more power and less pitching (rolling) in the ski as your paddle.
• Imagine that your hips and shoulders must rotate together, as one unit (I notice that your shoulders rotate more then your hips, very common mistake). This establishes your whole body connection the ski and also the water, and will help you turn yourself into a powerful lever.
• Imagine that your "push hand" is actually your push shoulder (which is rigidly connected to your hips). Your hand shouldn't actually push (which makes the shoulder joints vulnerable due to extension and torsion). But if you push and pull from the core, it protects those muscles and joints and delivers far more power.
• Experiment with your hand pause timing on your catch hand, really let the hand float out there a while to allow your push hand to get into position and then smash the catch aggressively down (think of a pole vaulter).
• Maybe bring footboard back one notch, and tighten up your foot strap just a bit (also, suggest paddling barefoot to get a better connection to the ski).
• Finally, experiment with your paddle exit timing to help solidify some of the tweaks above.