I have set up a monthly mailing list service and listed about 15 certified subscribers (from past issues of the newsletter) and an additional 55 new potential subscribers. The report states that only 16 were sent out and that 14 opened the request. Why were only 16 "sent out" with seventy listed individuals to receive the newsletter.
Secondly, can we embed a video or add a picture to the Newsletter?
The newsletter is only set to people who have completed the double opt in process.
It isn't clear from your post but I am assuming that you mean 16 newsletters not 16 opt in requests. That sounds as if only one person from the 55 had opted in by the time the newsletter was sent.
Opt in requests have a high attrition rate and are often blocked by spam filters. If these are addresses that you have loaded yourself (again trying to read between the lines of your post) I think you will be lucky to get acceptance in double figures even if they have expressly asked you to be on the mailing list.