That sounds about right for an uncompressed version of 1080i. It runs at a little over 200 MB per second, so doing the math gives about 120 GB per 10 minutes.
Regarding your deliverables, does “most” computers for QTime mean most recent ones? Use H.264, at a moderate data rate (maybe 1000 K(bits)ps), and a frame size that seems compatible. Testing will be required. If it means older computers as well, you may need to try a less demanding playback codec.
DVD-video has a maximum data rate of about 9 Mbps for the audio/video portion. You probably can’t see a difference over 7 Mbps, even with fixed-rate. How much will fit depends on how long your video is (math may be required). And, to be accurate, you will actually downsample to 480i. 720 is still HD.
-jeff