Ok, click on profile picture is the kitchen.
Very nice!
Lovely!
THEY thought they should downsize for mobility reasons
YOU helped by finding a nice house
THEY decided to sign contract
THEY changed their minds
THEY decided not to fight the sale and to go through with it
THEY decided they don’t want to rent even though they have landlords in the family to help
THEY payed cash and have plenty of money.
Not your fault. You need to put that aside. Really, you do. They are adults and are making their own decisions. They probably have little else going on to consume their thoughts so this is a big deal to them. Problems loom larger when your life is smaller. The problem becomes a little tornado in their home and when you walk in you get sucked into the vortex. Step out of the vortex.
It is nice of you (and over and above) to go weed and help with the new property. Your H should let them know this.
Again not your fault. You helped out of love and care. NOT YOUR FAULT.
It will get sold. Life will go on. They will need you, your good intentions and your help in the near future. Don’t exhaust yourself with this.
Good thoughts
Great post sax. OP, please take this to heart. Maybe step back from your current level of involvement. Take a break and refresh yourself mentally and physically. You will have opportunity to help again in the future. But maybe you can choose to wait and let your spouse or his siblings step up and take a bit of the pressure and push back from your in laws in the next round. Let one of them be the bad guy. The house not selling will not make your inlaws go hungry or get them evicted. And who knows what may happen with worsening of physical issues that force them to move after all.
^You guys are so right. I just have to smile and nod and take a deep breath. Will be spending a lot of time with them all in the next week, so I just need to keep reminding myself of sax’s points. Not my fault. Not my fault. Not my fault.
Glad I have someplace to vent 
Yes, NOT YOUR FAULT. I notice elders have a harder time making and sticking with decisions, especially when they involve change and especially moving. Theybalso tend to blame folks for any poor choices THEY make.