I believe the problem is solved! Looks like I was having the same problem as Neurovore in this thread.
The issue seems to be NVSR (New Vegas Stutter Remover). It's not extremely clear in the install instructions unless you read carefully that users of the 4GB NV loader need to modify the following values in NVSR.ini:
With these changes my game runs as smoothly as the day it was born, load times are ridiculously fast and it hasn't crashed once.
Thanks to everyone on this forum for being so awesome and helpful!
MetalPhilosopher's post in Constant Freezing... Is this normal? was marked as the answer