Gotta echo what DDF2 is saying. You start the point with a stance that is low and wide enough, but once the point is underway, you play too upright. This does makes some other aspects of your game suffer. When you go for a BH topspin, you tend to bend backwards to generate your torque to make the shot. Sometimes it doesn't land, and when it does, you have to take like two steps to recover and you are in a bad position to continue the attack. When you are too upright, you cannot move to position at all, when you do move it will make you off balance, out of position, and off time - three strikes against you for consistency already. Playing upright makes you want to go for balls that are not really good chances. The result is way too many unforced errors and I think a lot of your issues come from this with some other things. You got a grip on combination shots, like a BH topspin and a step around to do a FH finish, but the lack of balance and poor stance interfere with a lot of this making it even more inconsistent for you.
What can you do to fix this? There really isn't a quick fix ! You prolly already know you are upright, so you probably got awareness, so it is a matter of being conscious of it and continuing to use practice and practice matches as a way to reduce and later eliminate this. You will likely not get to the point where you want to be in this the first few months, some take a few years, some never get it and remain an average or poor level.
Another thing I see you can control is your shot selection. Vs the second opponent USAK who appeared to use pips or at least a Balsa blade and blocked a lot, you chose fast attacks right in his blocking zone instead of slow, deep spinny attacks on 80-90% of your first attacks. He blocked you down on a lot of those as your balance issue from bad stance showed often. You also were expecting a better result from your attack and were not in position or good enough stance to continue the attack and when you tried it wasn't a good result most of the time. Some points you were able to keep balance and make several attacking shots in a row and that is good, but you were not making that your normal standard. You know how to make a slow topspin, you did some of them. Maybe he was giving you some balls that looked like you could fast loop for the point, but you hit it to where he was prepared. Try vs USAK for a slow topspin and then make a strong smash or loopkill to end the point.
You got a long way to improve you level on serve area and that is good, it just means it can only get better. When you are able to use the same motion (also have several different motions) and make every spin, break, depth, and pace possible, that will help your 3rd ball a lot.
For now I keep it short, the big three things you can get to payoff for you if you improve these are STANCE, SHOT SLECTION, and SERVE / SERVE RECEIVE areas.