Clearly he shouldn't have driven into the side of you and the accident is his fault, but something I don't understand is that you appeared to know that he wanted to change lane and there was a good chance that he wanted to change lane in order to go straight on. At the time he started to change lane he was in front of you and could have done so without an accident if you had lifted the throttle a little, but instead you used your horn and appeared to floor the throttle presumably to prevent him doing what he wanted to do, then knowing that he likely wanted to go straight on you accelerated around him blocking his path.
Why did you not just let him change lane in front of you instead of using your horn and accelerating to block him?
I don't know if you can see it in the video, but there is a large concrete barrier on the left side of the road, and i think some orange construction barrels, too. Even though the lane is wide enough for even a big-rig/lorry to easily drive through without crossing the centerline, many drivers seem to think that their car is a thousand feet wide, so they go WAY around things like barrels/cones/etc. I figured that's what he was doing, so I honked to let him know I was there. I am quite used to driving small cars - my other car is a miata, which is basically invisible to big vehicles like that tundra. honking, speeding up, moving further way to get out of blind spots - that all comes as second nature to me no matter what i'm driving.
I did not accelerate - he slowed down. I think you can even see his brakes come on when I honked. Then, to make myself more visible, and to give him space, I moved to the right, up against a barrier on my side - you can hear me running over the reflectors with my right tires.
Since I am not a Betazoid or any other telepathic life form, I had no way of knowing whether he would turn or go straight. Plenty of people, myself included, don't use their signal when in a turn-only lane. It's not really necessary, especially in an intersection like this where there are at least 2 different signs (one visible center frame at beginning of video, another visible hanging between the traffic lights, easily seen in the video as we approach the intersection and when we stop after the crash) plus the large arrow and the word ONLY painted directly on the road to indicate left turn only. plus there's no oncoming traffic that you need to inform of your intentions.
Also, if I had tried to stop to let him change lanes, there's still a good chance he'd have clipped my front corner, or at the very least, I would have then been holding up traffic behind me, potentially then being rear-ended. Houston drivers aren't always the most patient. Seen plenty of them pass school buses that have their red lights flashing and the little stop signs extended on the side. Sometimes they surprise me by being patient and polite - letting you merge or change lanes for example - but that's a very rare thing.