Hi Mike Up.
I can relate to your problems about reservations. Minnesota state parks just made 100% of their campgrounds reservable. That means NO first come first served. And even for retirees like us, we can get a site from Monday through Thursday, but the weekends are booked up a year in advance.
As for the campgrounds in Indiana, it may well be a problem in "da Region". I used to live in NW Indiana, and worked at both Indiana Dunes and at Hoosier National Forest. The Dunes State Park campground is almost always full. Have you tried the Dunes National Lakeshore Campground? The further south you go in Indiana, I think you may have less problems. Also fall and weekdays are generally less crowded, but it sounds like your work dictates your schedule. We retirees don't have that problem.
It is true that Hoosier National Forest has several campgrounds, but at least when I worked there (20 some years ago) they had no electricity. Also there probably are some boondocking opportunities along old roads in the national forest, but it isn't like out west. The Hoosier NF only owns about 28% of the land within its boundary. The rest is private land. So you really have to know where you are to not be trespassing.
Good luck to you. We'll be travelling through your state in just a few weeks with our camper. I hear the highways in Indiana are no great shakes (actually they GIVE you great shaking).