I know nothing about the I95 toll in MD, although I do know the I95 toll in Delaware is the highest, per mile, toll on the interstate system of any state.
As to where the money goes, it should be going for the maintenance of the roads and bridges. However, I know enough about how Maryland operates to know that you are absolutely correct in your assessment of where it will actually go.
The MD toll booth is just down the road a bit from the Delaware one (on the “going north” side). Both states want your money...BADLY!