Are temps causing shutoff or is it just unstable?
In other words what temps are you seeing when you are testing?
If you aren't using HWMonitor or another monitoring software you should be.
If temps are causing shutdown/throttling then yes a delid would help,
And hopefully you mean 1.37V not 13.7V
You'll need to up the voltage A LOT to see stable 5.3GHz.
Chances are you're going to hit the thermal limit FAR before that.
Last bit of info. If you are not using Prime95 version 26.6 you should be. That's the only version of Prime 95 I see anyone around here ever recommend for stress testing.