1. Don't worry about hitting the ball hard and focus on getting the motion right. Don't even worry about getting the ball in the service box - get it over the net at first.
2. If you want to copy someone's serve, copy Serena Williams' - that's a bomb-proof serve. John Isner's is a nice simple serve as well.
3. Have someone show you the Continental Grip because you are NOT using it when you serve, even in your "Tennis shit #2" video (if you can bounce the ball with your racket without cocking your wrist awkwardly, you do not have the continental grip). Yeah, it may feel weird initially and yeah, you will want to drift back to your old serve grip, but you should fight the tendency. Eventually Continental will feel natural on serve (and volleys).
4. Slow down your ball toss. Right now you're flinging the ball up. You want to gently place the ball where you want to hit it - having a straight tossing arm helps reduce variability. Practice the ball toss until you can get it to consistently peak at the same height and land at the same spot (place a bucket there to catch the balls). I suggest doing this with the correct shoulder tilt and racket hand up to reinforce the proper trophy position.
5. You need to simplify your service motion - there are way too many things going on and they change with each serve. Forget your feet for now, forget the backswing; start at the trophy position. Toss the ball then reach up towards it so that you are fully extended. (The first few times you might want to try to hit the ball over the fence - this is harder to do than you'd think specially as you have a tendency to let the ball drop too low on your serve.) You can play effectively with this kind of abbreviated serve. You can add the knee bend and hip tilt later on.
6. Don't think you can fix your serve in a matter of weeks. When my serve grip was changed from Eastern forehand to Continental, my coach and I worked on it all summer constantly adjusting and reinforcing the correct grip - and I didn't have near as many issues with my serve as you do. When my service motion was analyzed and compared to Azarenka's the worst the pro could say was that my knee-bend wasn't as deep and I didn't land as far into the court.
2. I'm not really trying to copy one at the moment, just get something in with a correct grip
3. I'm not bouncing the ball with the same grip I'm serving with. I know it's odd, but I'm just used to bouncing the ball that way. Of course, I'm sure the actual service grip still has issues.
4. I actually did that a bit yesterday. This is actually the improved version. I've always had major issues with ball toss.
5. Thanks, I'll try that
6. Yeah, I know it's going to take a while to make anything with even semi-correct form actually be acceptable as a serve. Yesterday I had 15 double faults in a 6-3 6-2 win
I'm planning on going to an actual coach in a week or two (after exams) and getting further help from him
Thanks for all the help by the way