My partially knowledgeable 2cents:
I’m thinking that the highways will not be closed at all and checkpoints are very unlikely.
We need to transport goods, from ports to cities. Especially food. The interstates are crucial for this.
There aren’t enough state police to do checkpoints on the interstates.
The state police do not want to encounter people unnecessarily and acquire COVID-19.
You probably won’t be bothered, but have documentation ready in case.
Restrooms can be a problem. But many gas stations have restrooms and I’m guessing some of these are open, or the gas stations will have a bigger sanitation problem.
Take along TP and if you can, nitrile gloves or disinfecting wipes. Disinfect all the handles you use in these places and wash well. Also bring hand soap, in case you find a restroom with none.
In a pinch, do what backpackers do. Stay away from water sources, find a remote location, dig a hole (when needed), and do your business.
They don’t allow you to sleep in rest stops. But Walmart allows RVs to overnight in their parking lots.