I will defintely say prayers for your family. My mom spent 30 days in ICU before she passed at 61. 2 years later my Dad died of heart failure and Hodgkins 2 weeks after having his leg amputated. I was 28 when mom died and 30 when Dad died. It was very hard an still is sometimes. My prayers go out for all of you and your MIL to get through it.
What difficult decisions your family has been facing. I can truly empathize with the life support piece. Nothing can make this time any easier except turning over your worries and fears to God and knowing that others are praying for your family to have its peace and health restored.
Please know that your family is in my prayers as well. I lost my DM when she was only 58. My heart aches for your DW. Sending good thoughts for her Mother's full recovery soon.