Dear Robin,
Sometimes what we perceive as negativity from someone else is actually their pain and grief coming to the surface. So try to let it bounce off your back or the weight of your own burden may become heavier. Telling someone to f off can ease your tension, but in the long run it can ruin your own character. Then you end up being a person you can't even recognize and never intended to become. And heaven help you if the person you're telling off is a guest! LOL
I personally try to stay away from social media, but find myself drawn here because I need to try and figure out whether Airbnb is a good fit and I learn much on this board. I think it was a good idea for the company to set this up as we all have something in common and can answer each other's questions from our own experiences. It can become as much as we need it to be and right now you need it to help you over a rough spot.
I too find having guests a pleasure, as they give me different perspectives on many things. If you can come up with more ways to interact with your guests, you will have less time on your own to dwell on your new circumstances. As an added benefit, it could also enhance their stays. It could be as simple as putting your welcome book in a drawer and walking guests through your property showing them how the TV remote works, where the light switches are and helping them sign onto the wifi. Or putting on the kettle and having a cuppa while you tell them about unexpected attractions in your area.
Your life has changed and it will no longer be a comfortable slipper (I loved your metaphor) that is a perfect fit, but it can become something else that comforts you. If you can only learn to compartmentalize your grief, because even though your wife is still living, you are no longer together on a daily basis, you may be able to discover what that comfort might be. Since your normal routine is in tatters, you might think about changing it, to include getting out of your home more often. Plan a routine visit to your wife, whether it be daily or weekly, so she has the comfort of your company and has something to look forward to. She has lost the comfort of familiar surroundings, so seeing you will be the highlight of her day. Volunteer with whatever organization you support, your church, a community kitchen for the poor, anywhere that you can do some good. If you don't have a pet, get one, or at least start feeding the birds in your garden. Living creatures are a great comfort. since my cat dies, I even enjoy watching the small rats that come to eat the bird seed (the cheeky little buggers are waking up early to get to it before I bring it in, so they will go elsewhere).
Good luck to you, Robin, you can get through this.