It sounds like you are probably in good shape. There is not a lot of testing you can do without something that understands DMX plugged into it.
One additional test I might suggest is to run a small sequence in vixen to just turn on and off a few channels. This will force vixen to communicate with the new dongle. That should tell you that your com ports are all set up correctly, your USB cable is good, and vixen can talk to the USB module on the dongle.
If you are going to have any issues with the dongle setup, this would most likely find them.
And one more thing
CONGRATULATIONS on your build.
-Jeff