For the 2nd point, jg4273 got it right! Anything you need to know about adapting a video file to dvd that site will tell you what's needed. The answrs are already there if yoiu're patient to search. The better quality of dvd burner apps such as by roxio or .... (mind block) are great & will convert your avi to mpeg2 in order to burn to dvd. Dvd's use mpeg2 format. If you're adding separate tracks to the one dvd then they'll seem lile separate chapters that you'd probably need to go back to the menu to play. There are joinder utilities that can be found at at the above site. Whatsmore it mentioned in every 2nd sentence lol
I've only 'just' started experimenting burning from dwnlded movies clips to dvd-rw. I normally work with full quality video & convert to dvd so ie; going down instead of trying to go up in size & compression.