Hi shubox56,
Assuming your mattress is placed upon an appropriate firm and flat surface/foundation, I would expect that the most noticeable “breaking-in” that you would experience with your mattress would be with the cover quilted to the wool (see post #3 here). All materials will go through this initial break-in period (even latex), but it would be unusual for an actual dip in the latex to result in just a few weeks.
As you already have a preexisting back and rib injury 
, unfortunately there isn’t a mattress that can be guaranteed to cure that (I wish there was!). As you’re probably well aware, issues in one area of the back impact overall alignment and can manifest themselves distally or proximally to the actual area of injury (such as a lumbar issue causing a change in gait or a change in the kyphotic curve of the upper thoracic spine). Beside the need for your body to adjust to a new sleep surface as well as lose some of its “learned alignment”, a new mattress can expose some of these “weaknesses” from your injury. Or maybe not. It could simply be an issue that the materials/comfort you’ve chosen unfortunately doesn’t meet with your needs. But I would certainly spend more than two weeks testing out any new mattress, especially with your unique circumstances.
Phoenix