Speaking of intermediate stops, you'd expect a fleet of 2000 ships sailing to Americas to be borne out of a maritime culture with a significant footprint. You'd expect said culture to leave some archeological traces in the Cape Verde islands, which are only 400 miles straight to the west of Dakkar. I have never heard of any hard evidence of massive Mali empire / West African fleets traveling to Cape Verde islands on a regular basis. According to Wikipedia:
> Before the arrival of Europeans, the Cape Verde Islands were uninhabited.[12] The islands of the Cape Verde archipelago were discovered by Genoese and Portuguese navigators around 1456.
It is almost impossible to sail North along the coast of Africa even for ships that can go strong against the wind.
This is what most people misunderstand about Columbus. He did not discover America, he discovered the way to go there and back which required sailing first South looking for passat and returning by sailing North and then catching western winds.
Columbus knew that (from studying reports) before he left on his first voyage, he repeated this four times as all sailors who followed in his steps did for 300 years.
You seem to take for granted the presence of New World in the mind of Columbus and that the only problem to be solved was securing the access. That is wrong. Columbus was looking for India. He descended to India's latitude and went looking for it westward¹. I'm not aware of any initial plans to return back to Europe on a similar manner, i.e. (this is a mere speculation but I'm inclined to believe that) he could have returned back by some well-known route, to minimize risks if he could find an actual Indian trade post, or anything familiar, really. Given the "unknown part of India" he'd encounter, only later it became a safer bet to attempt sailing back north-eastward.
¹ https://en.wikipedia.org/wiki/Voyages_of_Christopher_Columbu...
And that after his discovery this circular route became the only way to America and back used by other sailors. This is more of an achievement then placing flag on some piece of land.