I have to agree with Erik... Your swing looks much better than a 12 HDCP. You need to work on your short game (putting, chipping, pitching) - because with that swing you should be minimally shooting low 80's IMO... Which puts you in the 6 to 8 range for a handicap. So you really could be half the handicap you have posted (if not lower).
Here is what I would recommend...
1.) Start tracking your stats using any number of methods - conventional scorecard, or use an iOS or Android app. I use Golfshot and it gives me stats like below. Very quick and easy to key in the results from each and every hole. Then you know where your deficiencies remain.
Once you have your stats, then you can dial into your weakest link.
My GIR last year at this time was ~ 40%. And with all the swing changes I've been working on, I've been able to improve. I've been trying to get my GIR up to 55%+ on average (currently at 50.6%), and lower my Par 3 scoring average to a number closer to where I'm at with Par 4 and 5's (x.3)... Currently I'm at 3.5 for Par 3's. And while I'm getting closer - I still have room for improvement.
I believe once I implement the next set of swing changes - I'll hit those metrics pretty easily as my ball striking consistency should improve.
But I know I have more work to do around the greens. Only getting up and down 36.7% of the time is a glaring issue. But it isn't as much as my chipping / pitching... It really is my putting. Pressure putts - for birdies and par savers is where I struggle. I need to spend more time on the green putting.
Enough about my game... My point is that you have a solid swing - a foundation to play some great golf. Why your handicap is a 12+ is alarming.
2.) If you really want to split hairs on your golf swing... It looks like your swing plane on the backswing is too flat. Which causes you to swing on more of a horizontal arc around your body (too much so). I believe your plane should be a little more vertical. And believe if you work on getting the shaft more vertical at A3 - it should help - as on the downswing - your closure rate is high. Meaning you aren't keeping the club down the plane line for very long.
This Foley video helped me understand how to set the left wrist hinge at A3 - and get the shaft vertical.
Remember - stay connected with the backswing... If you stay connected - and set that left wrist properly - the shaft will get more on a vertical plane than you currently have.
3.) On your DTL video - the camera is too close. You need to move the camera back another ~ 8f or more. Other than that... Looks really nice nevrino! I hope I can nail your pivot like you have.