Booth escape route north

[L Verge]

I am quite sure that I will get my head snapped off for saying this, but - as much as I like Starkey's book - it stands more like historical novel than anything else to me. That said, as a native of the Maryland/DC area and knowing what the situation was here in 1865, I cannot fathom why Booth would even have considered going north! To make it even more implausible, why would we consider that he started out going south and then planned to make a U-turn?

First, he would have been heading into Union territory with a population that had held Union sympathies throughout the war. He must have known that the Feds would be searching his home territory of Baltimore, its environs, and Harford County. From that point on, it would definitely be enemy territory. Why head to Canada where the exiles there were in turmoil also? Surratt was close to Canada and also had the church to hide him, so it was a tad easier for him to hop across the line.

Then, Booth had spent months building up support in Southern Maryland; why abandon it? Why was Davey in Southern Maryland the day before if not to verify the route was open? It was open - the people still assisted the fugitives, though not warmly (except perhaps for Dr. Mudd). By the time Davey could reconnoiter, however, it was difficult to spread the word or gather the forces. Confederate Secret Line personnel had other issues - and no guarantee that Booth would succeed. Even to have remained hidden down here for as long as the pair did while being the objects of the largest manhunt in U.S. history to that time was pretty amazing.

If Booth did ride into Southern Maryland for even a few miles, where was his planned U-turn supposed to be to get him headed north? I know the lay of the land and where old roads existed, and it still doesn't make sense to me. I think we're grasping at straws to find new theories.