Moderator, if this is not the best forum to post in, please move my topic

I've searched the internet high and low and cannot find good information about developing a commercial website that sells long play downloadable (NOT streaming) video products. The reason I don't believe streaming would be a viable option is because the videos I offer are not "movies," i.e., watch once and then you're done. My videos are educational in nature and the student will want to watch parts over and over again, refer to it in the future, etc. In addition, the content is long play (catalog of 3 dozen tangible DVDs to be converted to downloadable videos) These DVDs range from 1-2 hour DVD-5's all the way up to a 2 set DVD-9 totaling EIGHT hours. All that in addition to the new content that will be created. I think the download-to-own model is the best way to go unless I've missed or not considered something about streaming that could make this work?

To make the download process easier for these long videos, I'm envisioning a backend account area where, after the purchase is made, the student can download the DVD chapter by chapter so that he doesn't have to download everything at once. Just simply break it down into digestible chunks. Customers are from all over the world so I believe a CDN would be necessary, perhaps making use of Amazon Cloudfront and S3 for storage?

The research I have done thus far turned up these sites/services that specialize in downloadable products:

Have you created this type of website before? If so, what would you suggest for a platform, or would something like this need to be coded from scratch? Wordpress? A particular shopping cart? I should mention that I'm not a coder and I'm actively seeking someone to develop this site.