Here's an idea: without the economic and demographic collapse of the 1630s and 40s, you get a stronger Qing. There's still the Jurchen threat to the north (the "Great Jin"), and there's still the Little Ice age and the Shaanxi Earthquake, which convinces enough people that the Emperor has lost the Mandate of Heaven. There are rebellions, but the Qing crushes them, retakes the northern cities lost to the Jurchen, and in the mean time flushes out the wasteful and decadent bureaucracy that accreted around the Forbidden City in the early 1600s. By the end of the century, you have a newly revitalized Qing, with a fully quelled populace, a streamlined government, and veteran armies. By the time the Portuguese get to the Philipeans, the Qing are ready to leap on a new opportunity.Maybe there will be less mismanagement, though, of the economy and of natural disasters because of the economic effects you've mentioned.
Those ex-slaves to be armed by the Spanish to fight the Portuguese, and by the Portuguese to fight the Spanish. I like it! They could just establish their own state, but what if a local would-be Monteczuma hires these well-armed foreigners as an imperial guard?like, maybe let's have some French corsair initiate a huge slave uprising in Hispaniola or Cuba that leads to a large amount of ex-slaves escaping to the mainland.
So basically the Caribbean is so chaotic that /no one/ can reliably set up colonies in Central America? That will be nice for the natives inland, although I bet the people on the coasts will find themselves preyed upon by Portugal, Spain, and France as well. There should be some interesting communities growing up around ports to see to the needs of the pirates.With Spanish Florida and Cuba, I think its going to be hard for the Portuguese to do much in the Gulf of Mexico... to interact with the Aztecs they'll have to go through Panama or around South America. That might not happen until the 1540s or later.
When does smallpox reach the Incas? Assuming that there /is/ a war of succession, Atahualpa wins it. Rather than being caught by Pizaro in Cajamarca in 1532, Atahualpa makes it back to Cuzco, where he cements his position. By the time the Portuguese impinge on his empire, Atahualpa might be an old man, or he might be dead, and a headstrong new successor will be in charge. I suggest the first option will result in at least initial peaceful trade, but the second might give us war. I suspect Atahualpa's successor will lose that war, but maybe a rump-state hangs on in the northern part of the empire (I'm assuming the Portuguese attack from the south).
Lutherans: I think there will still be grievances in Northern Europe against Southern, but without potatoes to give the North a decent population density, Berlin and London will be backwaters compared to Rome and Madrid. If there is a Reformation, it will fare badly indeed. Maybe Northerners better their chances by requesting the help of the Eastern Orthodox Christians. They won't get much help from distant Moscow, but the Patriarch of the Autonomous Millet of Greece convinces the Ottoman Sultan to make common cause with Middle Europe and Scandinavia. After all, they have open sailing routs to the Atlantic, and there's this lucrative new continent waiting out there...