If I remember correctly, I calculated it out to be about 7.5k exp for 750 CP, or 10xp for 1 CP. I don't know if that varies by level / mobs, but I would imagine not.
So, for 40k CP, you'd need 400,000xp. That's a whole f_ckload of subjob levelling. You could also go the route of trading crystals to Gate Guards, but the cost to get 40k CP would be just ridiculous.
Dying in a region with Signet on will decrease your nation's rank in the region, but will not cost you CP.
If you switch nations then switch back to your original nation, you will still have all the CP you originally did (confirmed this when we spent all of an LSmate's CP prior to her switching; she was then told by the embassy that her CP will remain in a bank for her).
Edit: hooo! If Mariox is right with his numbers, I'm way the eff off... then again, it may have to do with who's nation controls the current region. I didn't pay attention to that when I was calculamating.