I'm sorry that I don't know more about your Sightseer but if you could post some information about your engine and chassis those of us with similar setups might be able to help you better.
I was able to obtain a wiring diagram for the chassis portion, including the engine, from our chassis maker. If you had a similar wiring diagram, you could probably identify the circuit for the failing fuse and that would tell you what components are being affected. Often, with that much information, several possible repair items can be identifed.
The fact that your steps don't work is puzzling. I wouldn't expect the steps to be on the same fuse as anything which controls the engine. If they are Kwikee steps, you might consider carefully going underneath and unplugging them and then replacing the fuse. Your ignition switch is the common point among your symptoms and you may have a problem there. I can see the back of my ignition switch from under the dash. If yours is similar, you might consider shining a flashlight on it to see if anything looks burned or loose.
Those are just a couple of thoughts I had based on the information that you provided.
2000 Georgie Boy Landau 36' DP
2005 Saturn Vue toad