The length of video you can fit onto DVD is not really the question. It is all about bitrate management. To put things simply the higher bitrate, the higher quality, the more space taken up on the DVD. What you have to do is get the best encode you can for the lowest rate. It is a trade off and only you will decide what is good enough for you.
The maximum rate you can use for video & audio combined is 9.8Mbs
If you are using compressed audio (Dolby digital) this will typically only take up about 0.2Mbs of that rate.
If you are using PCM uncompressed audio you will be using up about 1.6Mbs of that rate.
From those figures you can see that PCM audio is either going to have to mean your project is shorter or the available bitrate for video is going to have to be lowered to in order to accomodate the audio (quality of video will therefore suffer).
We are all looking for the perfect encode and the MainConcept encoder is pretty good (value & quality). For example CCE encoder retails at about $2000.
If you use CBR encode you are using a constant rate throughout your video. This is whether the encode will benefit from that rate or not. Where action or detail is minimal, a lot of that encode will be wasted & will merely be padding out the stream. If your project is under 1 hour using CBR will not matter much.
If your project is longer you could use VBR. This varies the rate between a max , & min with an average rate you set. The encoder should where there is a lot of action use more bitrate & where there is less give you a lower rate, but adhere to your average over the whole video. This will save you valueable space in longer encodes. Some VBR encoders do a multiple pass in order to efficiently manage the bitrate further. They will view the whole video first to gauge where action is high & low and then encode on a further pass.

You should get good quality enocde with an average of about 6.0Mbs for your video stream, though quality of source footage will play a large part in that.

Try rendering small sections of your file with different settings to see what is acceptable to you.

The file you have created would be too big for DVD. Your whole project in authoring program (not only MPEG files & audio but menus & navigation data) can't be bigger than 4.37Gb. Your 4.7Gb disc will infact only be 4.37Gb. Media makers measure Gbs in 1000^3, your computer uses Gb 1024^3.

If you want to use a formula to work out what rates you can use for bit budgeting look at my posts on this post

http://www.sonicfoundry.com/forums/ShowMessage.asp?MessageID=112432&Replies=4&Page=2