You don't say which revision of the Actiontec router you have.
As others have said, the NAT table is NOT an issue in the rev. I.
Any reference to NAT table issues with the Actiontec refers to GEN1 or GEN2 routers.
3) Simply put a router on one of the static IP addresses. Connect all your other devices to that router.
As other have also said, a business account is overkill. There is no need.
If you're experiencing disconnects, something else is going on.