Not much around Baltimore. Also in Baltimore, be aware propane containers are not allowed through the tunnels on both 95 and 895. You will need to go around on 695. Avoid Baltimore and DC at rush hour (am and pm)!!!!!
I have never stopped anywhere in that area (grew up just north of Baltimore) but IIRC there is cherry hill park campground
on the north side of D.C. near college park that you can see from the highway. It was near where 495 and 95 meet. It looks to be easy on/easy off on the map.
If you stay in DC you should be able to make south of the border near the NC/SC state line. Or you could stay in northern NC near VA border at Carolina Crossroads. This list from i95 exit guide for NC
might help you. You can cross reference it with RV Park Reviews - Trusted Reviews of Campgrounds & RV Parks
Here is the maryland version
I do know that Susquehanna state park is not big rig friendly.