Setting Up a Router. Should it be just used as a router or access point?

If your just using the router in a dorm room then you don't need to set it up as a wireless access point , you just need to set it up as a normal router and you don't want to turn off DHCP.
A wireless access point is to extend a wireless signal , so if you were in a big house and the other end of the house could not get the wireless signal you would put a second router and make it a wireless access point to extend the wireless signal.
 
It depends how many unique mac addresses the college will allow you to have plug into the jack. If they only allow one you will have to run the router as a router and share a single IP using the NAT and DHCP. If they will allow you to have multiple then just use the router as a AP. I suspect you did not configure the router to AP mode just turning off the DHCP does not make it into a AP.