Hello and welcome to the RTA forums !

You are right on the limit [a little over] of the distance we would recommend travelling over 2 days, but it can be done and Boise is about perfect for an overnight stop. I don't see the point of adding distance and time to your already long journey by going to SLC as US93/NV318/US93 will do just fine. It's not exactly desolate and there will be other travellers going through so just top your tank up in Ely and off you go !

I don't know of any reports of over enthusiastic policing in the area, but if you are not doing anything wrong you will have nothing to worry about. With regular stops, snacks and refreshments in the car along with basic tools and a properly inflated spare tyre in case needed are all wise items to carry. A maintenance check before you go and knowing your servicing is up to date is always reassuring. Check [replace if needed] fluids, tyre pressures [and condition], wiper blades, brakes etc.

Have a safe trip!