I've found that it's not only the fat content (by percentage), but what kind of fat you use. Our local grocery store will save all the pork trimmings and that has worked the best, but we also use bacon ends occasionally. You're right about the outside temperature affecting how easy or hard it is to regulate the smoking temp. Another aspect that I've found to affect the quality of the sausages is the grind of the meat and the fat. Courser grinds and grinding the fat at almost freezing temps seems to produce the best summer sausages, while the "snack sticks" seem to do better with a little finer grind.
Ribs are hard to cook consistently, period. They always either turn out fall apart in your mouth good or like an old Cocoran boot sole. I'm beginning to believe that size matters when you talk about grill size and ribs. Let us know how yours turned out...