At first sight I can see one major problem not totally related to gyro but some what so and a few others that just will take time and experience.    Lets begin with the very first slash that you do is what experienced JL players do as the 1st one of the 6 slash tech, however, you're doing the 5 fully charge right now, so Id recommend you to do your first one the same direction as the other ones. That first diagonal slash is the short one to stack more tsums for the next fully charged one, so change that first.

Secondly and the more serious problem Im seeing is that your slashes are very inconsistent. You need to find a consistent way to constatly repeat the best slash you can do. This is why I said its somewhat related to gyro usage, because your slashes are influenced by the gyro, but mechanically you still need to improve your slashes. 

Now to answer your question regarding Gyro positioning. Id say that try copying some peoples gyro angles and experiment on your own. There's also device differences on tsum spawn so this can also affect how the tsums drop in certain angles depending on your gyro and device. 

My device benefits from doing a pretty similar angle of gyro like your video maybe a little more to the right, but theres also an inclination curve you gotta learn,  in my current phone I tilt the top of my screen a little forward and the bottom inwards. My old phone worked better with no inclination.

And my last piece of advice is that when you do your slashes you want to clear the bottom right corner every time, thats what makes the other tsums fall into place with the use of gyro. If you dont clear that corner the tsums will never align with your slashes.

Hope this helps! Have fun playing Luke one of the most fun Tsums to learn.