Ken,
I'm so sorry to learn about your son and your wife's sister-in-law's dad!
Claire and I went through a similar trauma to yourself some years back when our older son had to be admitted into hospital. It was horrendous - but thankfully he recovered. Your son will, too!
Yes, life is hard to deal with at times - but I am always aware that there is someone worse off than me. That doesn't alleviate our problem at the time, of course, but when we get through the trauma we realise we are by no means alone. Wanting to understand the cause of suffering is one of the things which started me off on my spiritual journey. I quickly realised I was in good company - because that's something that started the Buddha off on his quest, too!
All good wishes to you, your wife and especially your son. ((((((((()))))))))
Ian