1. im not sure what happen. maybe you use plugin to insert youtube video. if you just paste the youtube plugin, it will work normally.
2. there is option to control this, please take a look right here : JNews : Header Option > Header – Mobile Option > Menu Following Mode.
3. i don’t really get this question, can you explain more about this?
But Mega menu only work on desktop.
4. im not really sure what is the problem. can you contact me from my profile page. https://themeforest.net/user/jegtheme