Sorry for my previous correction on the comment, didn't read your points very well. Now for the technique part:
1. COILING. You should keep more open stance, but your upper body (shoulder line) should be ~~twisted~~ not in line with your waist line/legs line. That way you will get more upper body rotation (so, stable power) without forcing it with your hand (uncontrollable power). The red line on the picture is how it should be.
TIP: try practicing catching the ball with your non dominant hand. Not by moving your hand, but by adjusting your footwork so the ball falls in your palm without adjusting your hand (it will lead to stable shoulder position untill the point of impact). After you get the feeling (after 10-20 balls), try changing "catching the ball" action with the hitting the ball by the racket at the last second.
2. JUMPING. Try listening to the guys who say "don't jump" to you. Not because it is wrong (all of the pro players do that), but because judging from the video, you don't have total control over the shot, and adding jumping action above your developing technique will harm you. Instead, always try to get under the ball with your footwork, and later, after you will get "that" feeling, you can practice jumping. It will add on to your shot naturally.
Also, try observing pro players, the most perfect technique of right-sided player in my opininon is by Chingotto ([https://www.instagram.com/reels/C6ZGrHpNyu6](https://www.instagram.com/reels/C6ZGrHpNyu6))
https://preview.redd.it/g1ozhenqo1ng1.png?width=468&format=png&auto=webp&s=088d82ad29b0489fecefcd526c2bbf75aa6f5594