Be firm and send your ex-boyfriends father a text telling him to leave you alone, you want nothing more to do with him and then either block his number or change your number.
Everyone on here is right, he does not love you and he will NOT leave his wife, he just wants a quick fumble when it suits him. If it ever got out you would be known as that girl who split up a family because you were mucking about with a married man. All of the family will hate you, all of their friends will know and hate you. People will gossip about you, men will think you're easy. If you think its tough now, it will be a lot, lot tougher if it gets out which it will at some point if you carry on. When it gets out, he will be away from you faster than you can blink, he'll be trying to win his wife back by spouting sh*t to her hoping she'll believe him, you will be forgotten and on your own. Do you really want all this?
I'm not being mean, I'm just telling you what will happen. So, if I were you I would step away and be grateful you weren't caught out, forget about your boyfriend too because you ruined that when you snogged his Dad. Move on