Absolutely. Why would he speed at 3X limit for 20 miles while having a snit fit and evading the law if she had slapped HIM. He was trying to get away from the eyewitness guy who had STOPPED. Reading between the lines (IE IMO) she was in the cafe finally uploading her work, it was slow going on an afternoon with shared WIFI, he was having a fit because it was his turn to go hiking and he had been twiddling his thumbs all day while she was at work trying to finance their trip, IMO he may have turned off her upload, told her she would never be a success. She says wait. I need to upload my work, he says, Then walk, I'm taking the car, and he starts hitting her when she objects. By the time he speeds away, thoroughly breaking several possible felony laws, they get pulled over. He adopts his manic-style babbling shmooze, while she is so upset she still is taking the blame for everything. Unfortunately he is right there for future punishment if she says the wrong thing. IMO
He didn't speed for 20 miles. The route from Moab to the Arches entrance is mostly 55-60. The off ramp is the only place with the 15 mph sign and that sign doesn't appear until partway off the offramp - it was that 15 mph zone where he was going 45.
It is not 15 mph all the way from Moab to Arches. He was driving erratically on that offramp, though (hit the curb or even went over it and then back).
I figure he was controlling about the VanLife uploads - he wanted the money from them, she wasn't doing it fast enough (she made progress that day, but it is very time consuming to edit, add sound, and upload travel youtubes).
Gabby herself says he disparaged her work (probably after urging her to do it, then getting annoyed that it took actual time). He doesn't seem to like being in the town of Moab for that long, even though it's a pretty interesting place.
She admits she hit him too. What felony laws did he break by driving away? No report says he was speeding at that point (why would he wanted to be arrested within city limits?)
I agree that his style of speech is quite problematic, and while not exactly manic, it has a quality to it that is almost too calm. Almost flat. At first I thought this was BL's version of trying to look like the calm, sane person in the situation. But I think it's a lifelong pattern for him to explain away his temper in this way (by being super calm and reasonable-sounding). I think he does have some kind of mental impairment (nothing to do with knowing right from wrong, though). I'm basing part of that on the books he mentions in his SM.
If he was so upset about the time it took for Gabby to upload, he could have gone hiking earlier in the day - a treasure of places within 2-3 miles of Moab, really. Instead, he chooses to lurk around her. There are great places to hike just by walking to the edge of Moab. Like Mill Creek - starts 10 minutes from the CoOp.