The crash when opening saves on mac is definitely something to do with the threading, and i'd rather just test this first to see if it fixes it
Copied from my mod almost entirely as-is, with the changes to HTTP.cpp included, also added locks into Download.cpp even though it is probably overkill
something is up with the pthreads library (dynamic compiles still broken), probably windows libraries all need to be recompiled and distributed separately like I did for visual studio