You did the right thing by texting to see how the FIL is doing. He's been there for you and your wife for 17 years and you don't know how much longer he's going to be around. I don't consider this particular situation as cake eating...I consider it a necessary trip for her to check on her dad and you being supportive of her during this time.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
