A fake escape was meant to be staged, but Dolarhyde intervened himself before it could happen, and killed the police, allowing both Hannibal and Will to actually escape so that he could 'change' them himself (as he needed more privacy than the middle of the road would allow). I don't think it was meant to imply that Will told Dolarhyde everything (but if he did it would be entirely fitting, I just don't think another scene with Dolarhyde was necessary to imply this with a basis in the show), but I do think he definitely expected Dolarhyde to intervene (note Will's conversation with Hannibal where Hannibal calls him out on it being too easy, note how Dolarhyde has a history of brazen actions, and note how Will clearly knows that Dolarhyde is 'intrigued' by the thought of killing Lecter and having access to him). He certainly was willing to sacrifice the police though, he never intended to go through with the entire plan, that was a ploy to trick Jack and Alana into accepting it; Will was, as Bedalia stated, pathologically lying throughout the entirety of the episode to release Hannibal (including when he told Hannibal that it was 'bad' to see him again, when Alana would have been listening). Had Dolarhyde not intervened? They would have escaped together through another means.
Will didn't necessarily want both dead, Will never really wanted Hannibal 'dead' per se, he wanted to 'one-up' him to put it crudely (of course, in this relationship that regularly consisted of proving that he's able to outsmart, snare, and kill Hannibal). If Will ever truly wanted Hannibal dead, he was able to do it very easily in the kitchen after being released when he had Hannibal at gun point, but he didn't, because he wanted to see how it would play out and to prove that he was smarter. He wanted to prove his superiority, just as Hannibal wished to prove his (but more often succeeding). Will had, in many ways, moved on from Hannibal and this desire to prove superiority, but in coming back, his 'current' life was made unsustainable, and as Bedalia stated, he couldn't live with Hannibal (who was in prison, trapped away from him with Alana as a barrier), nor could he live without him (with Molly because of all that happened). Will finally embraced his ability to manipulate events through cold and cruel means, so that he could kill with Hannibal (note when Hannibal asks if he was surprised with Dolarhyde contacting him and indicating his survival, he says 'yes and no'. His motive for Dolarhyde dying only rested in the ability to secure his family's survival, but he himself noted that there was no future there for himself (it was an act of righteous violence, killing Dolarhyde cruelly to give Molly and her son peace of mind, while completing his transformation). Will, himself, may not have known whether he would allow Hannibal to live or not in the moment, but his conversations with Bedalia certainly indicate it was his intention to let him live from the beginning and to escape with him.
Dolarhyde attacking Will? It could be down to Dolarhyde hearing voices warning him of Will,, Dolarhyde having very sensitive hearing (fitting in with him being of such peak capabilities), or it could just be unexplainable and a contrivance to allow the scene to happen.
