I have the Ultra package that's supposed to provide 15 down and 2 up.Those are "up to" speeds, not guaranteed. Nonetheless, you should be doing better than 1 Mbps down.
DNS setting should be automatic or dynamic. That allows Hughesnet to set your DNS. They may decide to change it. Once you are past the Lan/router and dynamically into a third party switcher/router you can go to a fixed IP.
DHCP should be set to Auto.
You are not bound to using your ISP DNS server system.