WR, Your family wants to see you move on because they know that you are in pain and they do not want to see you hurting. Sometimes when someone is sitting on the outside of the situation, they can see more of what is going on, which may be the case w/your mother. You were too close to the issues and couldn't see what was transpiring. We all have done this.
As for telling them anything, I would limit what I say to them about the situation. If you need to speak to someone, come here or select one good friend to talk to about your situation. If your h should ever decide to return home, it will be much harder for him to face your family if they know too much about what he's done and continues to do.
Keep in mind...until they have walked in your shoes, it is very easy to say divorce him and leave him in the dust. I don't think that there is anyone that hasn't encountered this particular train of thought from others.
It is your choice as to whether you stand or toss in the towel. It is your life and only you can determine when you've had enough. Keep in mind, there is absolutely no guarantee that he will return. It's always a 50/50 chance that he may opt to continue moving forward and start over elsewhere w/someone else. Sometimes mlcers find it is easier to just move on because there is so much damage that would require a lot of work, work that they aren't willing to do.
WR, I would suggest that you keep your conversations w/family members to a minimum when it comes to your situation. The less they know, the better.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.