1: Yes, with proper sailing tackle he can go out and return. He is sailing out with the prevailing winds and currents, but against them on the way back. Apparently, he failed to acquire adequate sails, using square sails, not lateen, and probably the incorrect vessel, too big and clumsy. In his defense, he may have been the first European in a millennium to attempt the voyage.
2: If he returned with gold and ivory, you would see a rush to exploit the new access route. The growing nations in Iberia, Italy and France would definitely begin exploring the West African coast. I doubt you would see much exploration into the hinterland.
3: He must deal with the Mali officials and traders in the area. The Mali traders had established trade partners. Ferrer must develop relationships, learn the desired products of the traders and determine the values of various trade goods.
4: Ferrer may find access to the Gambia river and/or the Cape Verde Islands.
5: The expedition faced shipwreck, storms, uncharted coasts and new, possibly dangerous populations along the way.
This may advance the Age of Exploration by a century, or maybe not. European rulers were still consolidating their OTL realms.