Please forgive the direct tone fo the following:
Definitely, your seat is way too low. This means your legs are tucked up and move clumsily. Raise the seat and set it like a road bicycle seat, as described earlier in this thread. When you can ride, you may choose to lower it again.
Secondly, you are looking at the ground as if you are expecting to fall onto it at any moment. Look where you are trying to get to, and you are more likely to get there.
Your upper body is leaning forward, which means your backside is sticking out. That put the uni at a funny angle. Ideally, the uni should be as near to vertical as possible, and the way to achieve this is for you to sit up straight.
You appear to be using your arms for fore/aft balance. Fore/aft balance should be done through the pedals. Every time you wave your arms, you are throwing several pounds of weight about, and that is bad for stability.
You appear to be correcting your speed too often, as if you are afraid of the unicycle going too fast.
Try this exercise: get a broom or other similar object. Balance it vertically on your hand. Now walk without dropping the broom.
The ideal is that you let the broom start to fall, but not too far, then you keep up with it by gentle changes to your speed. However, if your hand overtakes the centre of mass of the broom, suddenly, you have to over-correct and the whole thing becomes jerky and unstable. That’s what’s happening with your uni: sometimes the wheel is almost overtaking you.
Do not be afraid of falling off. If you are riding smoothly and confidently, you will always fall off the front and land on your feet. If you ride over-cautiously, you are more likely to fall off, and sooner or later the uni will overtake you and you will fall off the back - which can hurt.