Hello, I am here with a problem. I have watched other peoples replays, and it seems that I have a very hard time getting as much power as other people do. I have tried a lot of scenarios, but this is my best one to date. Any help?

try to move your legs you know extend contract also move your chest and lumbar.

The most obvious powerboost would be contracting the other pec.
The problem in your replay is that you have no chance of accelerating because the impact is way too early. You can't gain much speed in that short distance.
After grabbing Uke extend your left pec and wrist to push him away from you. By contracting it again you can pull yourself into Uke with enough room and time for other joints to accelerate your attack.
You will hardly see people grabbing and attacking Uke right away anyway.
Normally I set up a stance which favors a fast chest movement before I go for serious attacking.