work..period.
Dave,
Sadly you have a collection of incompatible hardware there.
Your choices are as follows (in order of my personal preference)
Get rid of the MR814 and ditch the modem...Instead obtain the Netgear DG834G (or similar from another manufacturer). This is the same device as you have now but with the Modem bit built in. You should be able to get one of these for about £60-75
Obtain a modem with a RJ45 connector. These are quite cheap..about £30 ish
Scrap the MR814...use a linux box with the USB modem (assuming drivers even exist) and the USB Wireless dongle in HostAP mode to be a Firewall/Router/AP...but then you are using a noisy PC to do what the little box in solution 1 can do (that said there is no reason your main PC couldn't be that machine if you don't mind having to have it turned on when you want to use the laptop)