I think you might include a “bookie detail”. The idea of a Black Rider chasing the hobbits to the ferry comes from the book. In the chapter “A conspiracy unmasked”:
The four hobbits stepped off the ferry. Merry was tying it up, and Pippin was already leading the pony up the path, when Sam (who had been looking back, as if to take farewell of the Shire) said in a hoarse whisper:
‘Look back, Mr. Frodo! Do you see anything?’
On the far stage, under the distant lamps, they could just make out a figure: it looked like a dark black bundle left behind. But as they looked it seemed to move and sway this way and that, as if searching the ground. It then crawled, or went crouching, back into the gloom beyond the lamps.
‘What in the Shire is that?’ exclaimed Merry.
‘Something that is following us,’ said Frodo. ‘But don’t ask any more now! Let’s get away at once!’ They hurried up the path to the top of the bank, but when they looked back the far shore was shrouded in mist, and nothing could be seen.
‘Thank goodness you don’t keep any boats on the west-bank!’ said Frodo. ‘Can horses cross the river?’
‘They can go twenty miles north to Brandywine Bridge – or they might swim,’ answered Merry. ‘Though I never heard of any horse swimming the Brandywine. But what have horses to do with it?’ I’ll tell you later. Let’s get indoors and then we can talk.’
So he did not chase them dramaticly but he was there, and the comment about the bridge being twenty miles away is right from the book.
