you do not need to repack anything just make sure in the save folder is:
a folder named levelcache
a globals.lsf (the one you changed)
and a meta.lsf
then start the game and load the save. you will get a checksum error message (because the checksum mds is wrong) just click okay and make a new save.
the new save will have a newly generated correct checksum but is flagged as corrupted.
what you need to do is extract that new save (again from lsv to a bunch of lsf) and this time convert the meta.lsf to meta.lsx and open that.
find the line:
<attribute id="Sanity" value="False" type="19" />
and change that to
<attribute id="Sanity" value="True" type="19" />
convert it back to lsf.
stuff everything in the new save folder like we did with the original save and you should be able to load that save normally with your changes made and without an error message.
You could simply repack the savegame into an .LSV instead of running the game, saving, reextracting, editing meta.lsx and repacking the LSV.
Also, D:OS 2 also hashes/verifies meta.lsf, so the savegame corruption warning would still trigger after manually editing the Sanity flag.