I think the best way to bring your IL closer is to give them space. I am sure they are in shock right now and just digesting the news and its effect on their grand children. If you keep on doing what you are doing, being the best man/husband/father that you can your IL will see that.
Although nothing has been said I sense that my IL are routing for H & I. Although they are blood with H they are also blood with our children and want to protect them as well.
If your IL have been married for many years they know how hard marriage is. I am sure they have had their own struggles.
Give them time. Your W will continue to say & do odd things that your IL will see. You will continue to do normal things and be a great dad.
I continue to think moving out will help you save your M. Dont listen to the negatives, you are doing the right thing.
---- M 39 H 35 D5,D4 M 4 T 9 ILYBNILWY 5/18/11 Left 7/11/11 Divorced 12/1/13