Transfer of inventory and EXP from crashed world to new world

So I had a world I was doing pretty great on. My computer suddenly turned off due to low battery, which caused that world to become corrupt. I have been able to transfer the world itself to a "new world" via copying the region folder from the original world to the new world. My problem is I haven't been able to successfully restore my inventory and XP (been playing on HC and I was pretty proud of how long I've survived).

I have looked many places and they all say to transfer the level.dat files (I am assuming this means level.dat_mcr, level.dat_old, file that is named simply "levels" but is a DAT file). I have also heard that you should also transfer session.lock, and the "player" folder.

When I transfer all of these the new world the file will not show up on the load screen. From my tests it happens as soon as I drop in the file named "level" that is a DAT file. I was wondering if it may be that the level file is corrupt (and if so how can I fix it? The file won't open in NBTexplorer) or if I'm just not supposed to transfer that.
I am working with Minecraft 1.5.2 and its pretty much Hexxit with like 2 additional mods.

level.dat will be where, on singleplayer, your player data is stored (along with a few other things like world seed). If you open it up, it's likely that it's blank now.

level.dat_old should be a backup of level.dat. If you still have that, try copying it to your new world folder and renaming it to level.dat (replacing the level.dat in your new world folder).

I'd recommend backing up the files you have currently before you do much more. For example, if you have moved the level.dat_old to the new world folder then continued to play on the new world, then your level.dat_old will have been overwritten by the new level.dat.