OP - really sorry to hear about your woes. What an utter tosser for letting you in then hitting you. I'm local to the area so I know that bit well, some awfully selfish driving goes on around there, it's really bad with the 3 lanes into 2 - everyone wants to get ahead, nobody in the left 2 lanes does the 'merge in turn' thing. If you were merging in turn, he might not have had right of way - a long shot, but did you get a witness? There are tons of CCTV cameras in that area (no exaggeration, seriously it's nuts how many there are just before the mouth of the tunnel) so it may well be on camera. Do everything you can to get the footage, including filing a police report for criminal damage - did you call the police at the time? If it's on CCTV and he can be seen to wave you in, they should be able to see that you quite plainly have a case, maybe for criminal damage, maybe for dangerous driving. Someone on here might be able to give you some better advice if you want/need it, I think there are a few lawyers on the forum.
Gannet - whilst I do agree with your point that to err on the side of caution is the best way to avoid a collision, I don't think the OP was not being careful (my apologies if I've interpreted your post incorrectly!). Although there are idiots out there, there are also courteous people who needn't be feared. I let people past all the time, I also appreciate it when people let me past - I think it's generally good karma. In this instance the guy in the truck didn't sound like he was being vague about his intentions, it'd be a bit like someone seeing you and letting you walk past while you're carrying a round of drinks in a busy pub, and then smacking you around the back of the head because for him it's a bit of a laugh - it's the sort of thing that is completely uncalled for. To live life 'normally', I don't think you should always have to look over your shoulder, somewhere along the line you have to trust someone.