hi sir, i already check your site, the facebook image is no problem , with those link you post, it don't have any video or picture, so, wordpress don't know get what images for facbook share preview image.
if you want , i can create new 1 function to help you add default image with now video/image post.
this is can be 1 field when you add new post, or it can be 1 default for all .
your task i able done within 1hrs.
I hope copporate with you, pls contact me soon as possible if you want hire me. thank you !