I'm a bit new to the N7, so I'll ask you to forgive me if I'm mistaken in assuming that F2FS will breathe new life into it. Even stock, it was sluggish, and ran similarly to my old GNex with all of its NAND issues.
Edit: realized I had reformatted all to EXT4 at some point. Still can't get the thing to boot. I found some solution up earlier in the thread, which I'll try now and report back.