Fixing up a 1920 rowhouse - front wall - to insulate or not
An inch of foam and a half inch of sheetrock might suit your space loss/window frame issues better and still be a lot better than no insulation at all. Just use longer screws into the brick, and perhaps some adhesive to reduce the number of screws you need (each screw is a heat leak.)

Being in an attached row house, the front and back walls and the roof are the main places you need/want/should have insulation, as they face the world, not your neighbors' interior spaces.