I'm 61-going-on-30 with the re-invigoration of being able to spend lots of time alone in nature. I'm temporarily grounded with some parental care-taking, but hope to be back in the Rockies before summer is gone and to be at RTR in January.
Last year, I got in more than 6 months of solo vandwelling and loved it. I was mostly in Montana ( and I'm feeling jealous of Marie).
In the 90s, I did quite a lot of camping while living in that gorgeous state, so the idea of sleeping out in the boonies was not frightening to me at all. With a van to live in instead of a tent, it is even less so. I stayed in free FS campgrounds or at dispersed campsites along FS roads. Even the thought of getting "stuck" from a breakdown way out in the boonies does not frighten me from a survival standpoint - only from how much money it would cost to get me out eventually.
Last year, I had a blown-out tire while on a narrow road along the Little Blackfoot River near Avon, MT. Helena tow services were quoting me a minimum of $200 just to come and put on my spare. Luckily a local man stopped to see if I needed help. He is a banker by profession but lives on his mini ranch by the river. He ended up coming back with his small tractor and his floor jack in the shovel to help me out. And then a couple of his friends stopped to help, too. Mine is an extended van with a high top (used to be a wheelchair public transit van), so getting it lifted to change the tire was a feat! The next day I purchased Good Sam Roadside Assistance -- which is designed for RVers like us. One use would more than pay for the year's membership.
I had a midnight visitor once. A young elk in velvet who found my van ideal for rubbing his antlers and jostling me awake with my heart pounding. My air horn convinced him to move along.
So my philosophy is to be as prepared and as aware as possible and then just do it. Like Suanne and so many other solo women travelers, I do keep handy an air horn, high intensity flashlight, wasp spray and sharp cutting tool (like a big, fixed blade knife, a hatchet, etc.).
I very much second listening to your gut feeling about any place you might stay. When I'm going from point to point, I usually stay in truck plaza or Walmart or Cracker Barrel parking lots. Have never been hassled or felt unsafe (I do double check that overnighting is allowed).