You need to get the bar and your weight shifting back as the bar leaves the floor. As you can see with that bar path tracing, the bar immediately moves forward. Start the bar a little farther forward over your foot and when you break it, immediately shift your weight back toward your heels and push the bar back toward you.
You move into the bar a bit past the knees - stay back over your feet as you extend and open the hips up a bit more, i.e. get your shoulders slightly farther back at the top of your pull.
You make that 70 because you do such a good job of pulling under and staying so close to the bar.
On the 80, the above problems are just more pronounced because the weight has more influence on your position and balance. Again, your pull under the bar is good in the sense that you stay so close to it, but your body is moving forward from earlier in the lift, and that carries over as you get under the bar, so you're a bit forward, hence the miss behind you.
Also looks like in your overhead position, your shoulders are rounded forward a bit, which means your arms can't be in a solid supportive position for the bar - they have to be angled back a bit. Work on tightening your upper back and shoulder blades to create a better base for your arms and therefore the bar. That with the weird forward movement just stuck you in a bad spot and I'd be willing to bet that the balance wasn't so bad you couldn't have stabilized the lift, but the way it came down on your elbows and shoulders made you reflexively bend the elbows and bail out.
Also on the 80, you get a little tense with the arms earlier than in the 70 - you may have such a good pull under because that's what you're focused on. Be patient, focus on finishing the extension of your body a bit more, and only engage the arms to pull down after that bar has been launched.
Finally, the best part of that 80 video is the girl's face in the background.