There are a number of occurrences of careless or inconsiderate driving in the episode you describe: the other driver pulling out in front of you without signalling; you overtaking him when you had to exceed the speed limit to do so; you braking in front of him after overtaking; him �tailgating� you (presumably at 70 mph); you �accelerating to a safe distance�. And I presume whilst all this was going on, the inside lane was occupied or, of course, you would both have returned to it as you should have done if it were clear.
I may be wrong but it seems to me that you did not like what he had done to you (pulled out without indicating) so you overtook him, slammed on your brakes in front of him and he then stuck to your rear bumper. All very sensible on both your parts.
I doubt that any of this behaviour would support a charge of dangerous driving, although from your description dangerous is certainly what it was. Any one of a number of the actions undertaken by the two of you could well have caused a collision. It would certainly be worthy of a charge of careless driving against both of you, him for pulling out in front of you and you for your overtaking manoeuvre.