Also not perfect, but you can put the combo with the other information you have describing all your bank accounts/passwords etc. Encrypted with a password on your computer or in your safe deposit box--something like that.
They won't lock from the inside generally, but I'd hate to have a kid crawl inside then have some responsible adult come along and lock it w/o checking. I'd keep it locked when not in actual use.
Don't store your ammo in the safe with your guns.
The sentry firebox should keep stuff protected a lot longer inside the gunsafe in the event of a fire. It's probably more than simply additive protection, since the inside of your gunsafe won't reach the outside fire temp for quite some time.