What you are going through is extremely hard. Can you have a family member come stay with you for a little while or can you go with your kids to visit your family for a week or so??
I would look into 12 step programs in your area. While AA/Alanon might not apply to you there may be others that fit your needs.
I have found new friends with Alanon. Woman that are going through their own messed up sitchs (not like mine per say) but just messed up sitchs so I feel more relaxed talking to them and being honest.
I think what is critical right now is that you do not show your H that you are upset by his confession. That you are cool with him dating who ever and you will be just fine.
Look I think your H is a big big AH but you should vent to us and act like everything is honky dory towards him.
Regarding your BFF - I would distance yourself for now without confronting her. Give yourself some time to look at this, in a few days you will have a clearer perspective as to her role in this.
You need more support. You need to take care of yourself so you can care for your children. Go visit your family
I am praying for you.
---- M 39 H 35 D5,D4 M 4 T 9 ILYBNILWY 5/18/11 Left 7/11/11 Divorced 12/1/13