OMG, Larkin, sooooo glad you and wife were ok! That guy needs to go to prison for sure! To have one accident, flee and hit another head on, he was looking for death. Too bad he didn't achieve it! But, soooo sad for you and the other vehicle he hit previously. This is a really scary thing when drunks drive. When I slid into semi trailer on exit back in March, the drunk driver that also slid to the shoulder ahead, did something similar. He gunned it, got going the wrong way, went past me, hit 2 vehicles behind me on the exit ramp, spun, heading right direction, hit me and then slid backwards under the semi's trailer, right snugged up behind my car. Everything was pretty much slow motion. Then, the jerk had the audacity to say, "I didn't know it would do that!" DUH!!!! He was from the town where I live, .... he just didn't think he'd get caught.
Sounds like when it rains it pours for your life right now, but things will settle down. That's your "3", so things will look up now, and no more problems, at least I would hope! Good luck getting the back line figured out. Otherwise it's nothing for the courts, just get a surveyor both of you agree on, both pay half of his fee, and go with whatever he comes up with! That will settle it forever and ever, especially if you put up a fence to "mark the spot".