Tvheadend

Naming channels

After reading a dozen threads or so, I'm having trouble understanding how to name channels for the EPG data.

I'm a US ATSC user with a Cubox-i2 running OpenElec 5.0.8 (Kodi 14.2) and a Hauppage WinTV-HVR-950Q tuner.
Live TV works fine but I can't get the EPG data to appear. I've created an XMLTV.xml file using mc2xml.exe on a Windows computer and put it to the cubox on a flash drive. In Kodi>System>Settings>AddOns>Enabled>Services>tvheadend>config the XMLTV file location is set to the usb drive. In Kodi>System>Settings>Live TV> EPG, I've reset the EPG database and rebooted several times.

I understand that the channel name in tvheadend needs to be the same as that in the xmltv.xml file. In the tvheadend web interface, under Config>DVB Inputs>Services it lists a Channel name and a Service Name, neither of which seem to be open to editing. Under Config>Channel/EPG there is a channel name (that appears to be open to editing) but they alread look like the xmltv.xml names. The drop-down list under EPG Source is empty.

What does the vacant EPG Source field indicate? Does that mean that tv_grab_file isn't reading the xmltv.xml? Should the channel name in the xmltv.xml file be the same as the channel name or the service name in tvheadend? Or something else?

I'm sorry if this is too many questions, but I'm not sure where to start.
Thanks for any help/suggestions.