Yes,
A gateway is just a device for getting from one subnet to another (or to the internet) so any device connected this way that has the ability to route is considered a gateway. This really isn't the standard though, unless you have a web filter.
Yeah, all my experience has been with Windows DHCP, and you're right, configuring the DNS suffix and other options are easy as pie. On the pfSense/Linux side it's a bit...different...!
I don't have much experience with pfsense. I've played with it a little but never actually set it up and used it. YMMV
