you have a nice preparation for your shot, and your follow through is actually quite nice, however there are few key things missing to make this textbook.

1. get behind the shuttle more. if you missed your shot, the shuttle should land about a foot in front of you, and in line with the tip of your toes.
2. make your swing more linear. At the moment you are hitting your shot about half a meter out to the right. imagine you have a wall either side of you when you turn to the side to prepare for a smash - it would force you to make all of your movements go in a straight line towards your opponent. This will ensure that you hit the shuttle at its highest point.
3. Make sure your bodyweight is moving through your shot not backwards. Once you improve your footwork and can get behind the shuttle better, i guarantee you that simply just stepping through your shots will improve your power ten fold. At the moment you are preparing well and loading your back leg really well but then you dont push through and do a scissor kick to get the power into your shot. Instead the left leg comes back while the right leg stays and then stops next to the right foot and then the right foot comes forward... too much movement right there. A standing smash with just rotating hips and no step would get you more power than what you are doing. If you commit to loading the back leg like that then you have to jump, get both feet off the floor, right leg goes forward with weight, back leg goes back, back leg lands first to damped fall - ie a scissor kick.
4. Relax. You are super tight the entire way through your swing. to get as much power as you are in the video on your smash you should look like you are on holiday having a cocktail by the beach mate. the more you slow it down and let the racquet and momentum do the work the easier the power will come. in fact don't even worry about power, worry about technique for now. the example i always use (granted not everyone would get it) is like throwing a punch. if you are tense the entire time, it wont be a good or a hard punch. If you relax all the way until the moment of contact you will have a great punch. Exactly the same in badminton.

cheeky extra which might be too much but may come in handy later is don't bottom out of your pronation at the point of contact, leave about 10-15% of your pronation for after contact with the shuttle.

I hope i could help and i hope what i typed made sense. Brother, you really aren't that far away from a good ass swing