Dear Rick Searle,
Pythagoras versus Mad tailor explains the subtle difference between the weak and strong MUH. You propose the weak version, "We live in a mathematical structure that is fully homeomorphic with a language of mathematics that retains ......Platonic features". A still weaker version can be obtained by replacing 'homeomorphic' with 'dictated by'.
Regarding the question 'where the mathematical truths reside', I agree with your third 'option', "all mathematical truths, including undiscovered ones, can be said to be embedded in the range of possibilities that emerge one once defines some set of constraints".
"Yet we're still left with a big question; namely, what is the relationship between this mathematics and the world it so accurately describes?" I think the above referred third option is the answer. First we define the set of properties of matter. Mathematical laws will dictate the final emergent structure, the only structure possible. The reason: the physical world has no laws of its own, it has only some basic properties, the laws that it follows are mathematical. The same is applicable to chess: we decide the arbitrary properties of the chess-pieces; mathematics decides the emergent structures. I invite you to read my essay A physicalist interpretation of the relation between Physics and Mathematics.
Matter has only four basic properties: mass, volume, energy and force. We do not know why it is so. This four variables can lead to a single final structure - refer my site: finitenesstheory.com. Chess has six variables and it leads to a large number of final structures.