Did your MIL whip her phone out and show you? Please tell me she didn't. Agreed with HW and ST. This is a very painful situation you are dealing with right now and being around those people only hurts you. I understand that need for some information even though you know it will only hurt, but you need to get back to that place where you were content and settled again.
Right now its not your responsibility for your exinlaws to see K. That is H's job. Let him do that on his time. Cut off contact for awhile and focus on the wonderful woman that you are.
Love ya!
Me: 46 FWS: 36 Married and Divorced 4/07, Pregnant 7/07,False R 7/07 Baby Girl born 3/08 Kicked him out because OW: 7/08 5/10 He realized what he had and lost. Moved home! REMARRIED 3/14/11!!