Crete, Cyprus, Algeria, Greece, Egypt, Iraq, and Syria were and/or currently are sugar producers and exporters. There's insane amounts of land that could be transformed into sugar producing areas.
No. The Ottoman Empire during its classical era always generated food surpluses particularly in citrus and other fruits. In the later empire its economy was more or less entirely cash crops as its manufacturing capacity was eroded through free trade.
I kind of want to talk about this point a little and then digress from it.
Some of the general themes on this thread have been implying that the Europeans came up with something new, remarkable, economically decisive, and unusually cruel, sometime after the discovery of the Americas.
That's just a very odd way of looking at it. What was the context of slavery in the period as western/Mediterranean Europe started pulling ahead of the world in sailing, which incidentally led to the Americas?
Well, millions of people were enslaved. It was normal; the past was mostly terrible, in case we forget that part. Nobody was inventing a single thing when they bought the slaves in Africa and took them to Cabo Verde. Since the middle ages and onwards, the Mediterranean was a hotbed of slavery. Europeans were enslaved and traded regularly in Africa and the Ottoman Empire (even before the Barbary states got into state-sanctioned piracy), and Africans were brought to Europe by the earliest European explorers, from Guinea and from the Canaries, which was devastating to the Canaries, by the way. It would make absolutely no sense for a people who own slaves and are themselves often a target for slavers, to say, you know what, we don't like slavery and won't buy any slaves. Especially when all the major societies they encounter in Africa are themselves basing wealth and status on the number of slaves owned by the rich and powerful, and practice slave-taking warfare.
What was the nature of this Mediterranean slavery? Well, people seem to think that it was some kind of domestic servant arrangement or a system of mutual ransom rackets, but that was never the case. Plantation slavery was pioneered in the Mediterranean and the Middle East. The Islamic period left some parts of the basin not only dependent on the continued success of the latifundia, but also trapped from developing as a mixed economy by an early monetization which emphasized cash crops. 14th and 15th c. Iberia was already growing cash crops, and even medieval Spain was a source of things the rest of Europe didn't have but really wanted, most of which was powered by latifundia. To recap, in the 14th and early 15th c. there were lots of people enslaved by Europeans and living and working the fields IN EUROPE, and the explorers of the 15th c. would have grown up with that still on their minds. So once again, it would be completely strange for them to look at potential slaves and say, nah, we're going to behave completely differently from most other cultures we meet and our own ancestors and contemporaries and not build plantations and not have slaves work them.
The reason why the "In Europe" part of it declined, is, to my mind, sort of a combination of things that happened, some cultural, some economic, and both influencing each other. The main one is the decline of religious pluralism in Europe itself, with the expulsions of the Jews and Muslims. Since most slavery was done by one religious community to the other all over the Mediterranean, that expulsions got rid of both the slaves themselves (those who converted and were never driven out became serfs), and the people who were insiders in the cross-maritime slave trade networks.
That gap was filled elsewhere; on the Atlantic islands, at first, and then the Caribbean and the American mainland. New networks replaced old ones and only grew as technology became better and more reliable, but they grew only as a natural progression of the medieval context within which Mediterranean Europe already existed.
Because the Colombian exchange actually caused a massive population boon through the introduction of crops suitable for the African soils- cassava, potatoes, corn, beans, rice (in central Africa), and so on that meant population and population density skyrocketed.
The result in part was actually a large increase in war and the formation of increasingly larger polities over the 1600s in much of Africa. But the slave trade kept crippling stability and so state formation gives way to a resurgence of big man politics and localism.
Without slavery, and those big empires stick around, using their newly earned surplus wealth to reinvest in themselves and enter the global trade networks.
Not sure about West Africa itself, but the Kongo could have certainly been in a better shape if it was losing less people: they were losing so many that even their own kings were acutely aware of it. The Portuguese of course weren't necessarily interested in a stronger Kongo, so they didn't care about the king complaining.