Once that is entered, the mobile driver is setup. The installation should be waiting to enter that pin.
Enter your personal email address and a pin will be sent to it. During the installation, it will ask for an email address. Once logged in, scroll down and there will be a link to it on the right hand side of the page. This can be found by logging into your ePrintCenter account. On the Mac, you could use the ePrint Mobile Driver. There is a work around that will allow printing with basic options.
You can try using an IP address that is close to the Mac's, such as 10.203.4.105, but this could cause other issues as I have no way of knowing if any of the IP addresses are in use. I would recommend setting the printer back to defaults as the IP address from the Mac more than likely will not work on the printer since it is on a different subnet (network). Each device has to have a unique IP address or there will be an IP address conflict preventing one of the two devices from working at all on the network. Just to clarify, setting the exact same IP address as the Mac on the printer simply will not work. Unfortunately, the only ones that can resolve this for you is the school's IT department. For all intents and purposes, they are on separate networks. This is a Class A address that is borrowing several host bits to divide the network even further.