Alan,
As mentioned above, taking HD down to DV is not the best choice of workflow. At the very least, go to D1 and use 8 or 10 bit uncompressed. Your graphics and footage will look better. No you won’t be able to master this to DV tape via firewire, but then, that would be a shame to do anyway, as it is a lousy format for broadcast or mastering. For a couple hundred bucks you could get a Decklink card and go rent a Beta machine to master to, or you could export your program to disk as uncompressed Quicktime and take it somewhere that can make you a Digibeta master.
Have a wonderful day.