Bricked Galaxy Tab A. Help? Please My device: Galaxy Tab A 9.7 (SM-P550) 6.0.1

So installed TWRP via Odin
-success
Then I flashed supersu via twrp 
-success

Then I tried to flash xposed via twrp
-fail

What I think happened was that it was the wrong SDK. I was supposed to install SDK 23 but I installed 21. So then what happened is that it failed and I tried to reboot back into the system and now all it does is reboot back into the TWRP menu and I can get into the lockscreen. So I tried formatting the data, factory resetting, wiping Dalvik/ART Cache and the Cache and tried repairing the file system and still can't boot into the lockscreen.

Please Help
Wiping /data and /cache of course won't help because Xposed writes to /system.

EDIT: As @DeathMaskSalesman points out in the comment, you should try the Xposed uninstaller available in the official Xposed thread. If that succeeds then great, you won't need to continue reading the risky part!

The Xposed zip shouldn't have allowed flashing on a wrong SDK at all, but now that the damage is done, back up data (internal storage) via TWRP first (you've already done a factory reset so I assume no app data needs to be backed up), then flash a factory firmware available at SamMobile with Odin to get a fresh start.