A big part of QBA 5 and accuracy is related to timing. On the 2nd and 4th videos, it looked like you rushed the throw. You were anticipating them coming open and rushed to get it to the receiver. That's your brain working too quickly for the game. By now, most people know what routes are going to come open on each play and so you already knew where you were going before the receivers ran their route. If you hold the ball just a beat or two longer, I think you'd be okay.
I believe the difference between 5 and 10 is that the game inserts a much bigger timing penalty. You really have to be precise and make sure your receivers are "looking" for the ball. On those two throws in particular, you threw before the receivers made their break. On the 3rd, it was similar, you threw as the receiver got to the end of his route and before he turned back around. Plus the penalty for throwing on the run. Compare that with the first video, where you held it and threw a step or two after the back made his break on the angle route.
Unfortunately, each of those penalties is amplified with QBA at 5 and there is no middle ground between 5 and 10. The biggest thing you can do is to hang in there and wait a beat or two longer for your receivers to get in and out of their breaks. That is counter intuitive because normally you want to throw as your receiver is coming out of the break, but that just isn't how the game is going to work on 5. There are still going to be a few what the fuck throws but I think you'll at least see a reduction in them.
Take an extra step or two drop, once your receiver hits his break, take a beat or two and fire away. It is a very slim window for throwing. Too early and you're going to throw the ball to Mars, too late and the DB will catch up and under cut the throw (especially on posts and corners). Normally I would say just rep it in practice mode, but you can't. Sliders work differently in practice mode than they do in OD. Really it just takes trial and error, knowing the speed of your receivers and how quickly they get in and out of their routes.
It also helps to start with high percentage stuff early on, I think QB 5 has a really big hot/cold penalty in there as well. If you miss big early, it'll just snowball on you.
Or just do what I do and run the ball 60 times a game.