I feel ya. You and I have roughly the same size hands and grip. I used a MX518, G5 and G400 for nearly a decade combined claw/palm grip but started to get pain in my metacarpal so I moved to a smaller flat mouse.
The Zowie FK2 has served me very well for about 5 years now with zero indication of wear. The closest I've gotten to a replacement is the Steelseries Rival 110 but I didn't like the hard plastic sides or side buttons, but this is subjective. This is after trying just about Logitech and Steelseries mouse available.
A FK1(medium)/FK2(small) or Rival 110(medium) may work well for you. As
mentioned the Ventus X looks good, I've been tempted to try the Ventus R model in the past since I prefer ambidextrous mice.