DVDs aren't "HD quality;" they're SD. You may have to lower your expectations a bit.
The simple solution is to send your sequence to Encore with Dynamic Link; Encore will transcode using the maximum bit rate that will still allow the video to fit in the limited space of a DVD. Select your sequence in the Project panel, and go to File > Adobe Dynamic Link > Send to Encore. The sequence will be sent to Encore and placed in a timeline; from there, you can transcode immediately or wait until it's time to build the DVD.