As far as using a dual monitor setup, in your configuration I would recommend using the built in Remote Desktop feature of Windows. You can run the "server" in a headless setup, remoting into the server from the client. This is rather simple to do, and doesn't require a lot of tech expertise to setup. This could potentially give you a dual monitor option for the server, although this might take some head scratching to setup, I honestly can't imagine it would be difficult. The key is to configure the "server" to allow remote connections. Usually done, from an administrator account, by right clicking on My Computer, choosing properties, and selecting the Remote tab. Under Win7, the options might be a little different. On the client machine, you must first install the Remote Desktop applet, and then simply setup a connection to the server. If you are using the Home versions of either Win7 or Vista, you may run into the limitation that Remote Desktop is not supported, or even available to install. In that case, go to www.portableapps.com
, and look for TeamViewer or RealVNC, both being third party remote desktop applications. Best of all, they are also FREE.
As for the USB dongle, that's more an issue with the provider. Those mobile connectivity USB sticks aren't meant to let you act as a server. They are only to get you connected to the web when you are mobile with your laptop. I'm not saying it cannot be done, but consider that your provider, a phone company, does not want their network clogged with traffic. Besides, the data costs would max out before the month was up. Your current data plan allows only so much traffic, measured in gigabytes, and that would top out very quickly in your scenario. Even if you were to accomplish said feat, the connection speeds would be even less than a WiFi, making any inbound connection to your server less than pleasant for those who manage to connect.
Certainly, the best recommendation for hosting a sim online would be to use a wired connection all the way, and a hosted server, versus a home setup using 3G, DSL, or even cable. Getting your internet service through the local cable company would provide the best connection experience, speed, and reliability. But again, using any provider that is meant for private home use in a "business" type setup will run into headaches. No provider wants a server connected to their network without you paying for it. This would be the same as any business running their website from their home account. The user experience would be less than ideal, and if the provider caught wind of it, they would complain, charge you more, and try to move you to a business account.