Thanks for updating this thread. It's good to know that it is working for you. You are doing the right way.
1.) If you want to add multiple videos, you might need another button. You cannot add multiple videos in one button link.
2.) To make youtube video play automatically, please add "&autoplay=1" to the video’s embed code right after the video ID (the series of letters that follows "v/").
<iframe width="560" height="315" src="
If you are using youtube link, just add the
&autoplay=1 to the link;
Hope this helps.