|It assigns the static public address to Computer1 (99.70.xxx.xxx)|
You seem to be getting confused between static IP addresses and dynamic IP address and public and private IP addresses.
A public IP address can only be assigned by someone that has had that IP address assigned to them by IANA. Thus usually means an ISP. A router cannot assign a public IP address, It would be chaotic if it could.
A private address is one that had been designated as such by IANA and they fall within specific ranges. Class A, B, & C. The most common is a class C address which fall into the range 192.168.x.x. These are the IP address a router a assigns via DHCP.
Private IP addresses
A static address is one that is entered manually, NOT via DHCP. An address obtained via DHCP is a dynamic address. It is called a dynamic address because it can change depending on the way the DHCP server is configured.
If I understand what you're saying, the router should point the public (99.70.xxx.xxx) to a new private (192.168.xxx.xxx), correct?
Yes, that's what Network Address Translation does. The public IP address shroud only appear on the public side of the router, not on a particular computer.
It sounds like you might have computer 1 in the DMZ, Not an ideal solution but sometimes necessary if the router did not have VNP pass-through abilities. but you say it has, therefore a DMZ is not necessary and is undesirable
You configure computer 1 to get a DHCP address from the router in the same manner as computers 2 & 3, then configure the router to pass VNP requests to that computer.
However, this is impossible with this router.
I bet you it does as this is the main function of a SOHO router. How are computer 2 & 3 getting an IP address? Is it static or DHCP? It cant be both.