In for a penny ... in for a pound ... is that what is said?
Question: php version on current production server is?
PHP 7 is true 64bit for your platform ... for the longest time Windows folks have suffered with 32bit PHP for years (32bit PHP on 64bit hardware). Wonder if current server, given it's current delicate state, could benefit by upgrade to PHP 7? You are already running a supported version of Moodle in 3.0.3 (or did I get that wrong).
Does Windows have any good tool like MySQLTuner for MySQL DB's?
I'll go a little further in making some suggestions for new box ... new box php 7. Record every tweak you have made to IIS, PHP, msssql for current production and put them in place even before you start to rebuild the new server.
And, while building new, look into 'poor man's backup solutions' ... does anyone make rsync for Windows? Thought newer versions of Windows now had availalbe for installing many of the tried and true Linux tools ... bash shell, etc.
Nice to hear you do have plans now. Do hope the easiest works and if not the least painful alternate plan. Best of luck!
'spirit of sharing', Ken