Unfortunately I can't tell you what's going on in your system. Debug the code to see where it hangs, wait to be sure that it's stuck not just slow, test it with more objects to understand whether it's a global problem or it's just about some specific objects, try to perform the steps (getting from TFS and importing to AX) manually and so on.
Regarding why it didn't synchronize everything, it usually means that some object can't be imported. If you can't identify it from the log, debug the synchronization to see where it fails.