Try this fix ( and on each layout you are developing): Enter layout mode, then change the fill color and font size while no object is selected. Then use the field tool to add a new field to your layout. Each field you add should now have the options you just selected. This should also work for adding fields through the other methods you describe.
That did it!
Thank you so much! I should remind myself to go here first rather than banging my head for an hour.