The rim sidewalls in the 1st photo look beyond dirty into more of deep gouges. I would purchase that Schwalbe eraser pictured or even use some silicon carbide wet/dry sandpaper on a block of wood and spin the rim slowly 360 degrees forward and back several times with like 240 or 320 grit. Then you could switch to aluminum mag wheel polish on a folded up little square of cloth and again apply the compound around the full 360 degrees to the whole sidewall (use valve stem as a reference) then reverse. Let the compound dry a bit then spin the wheel with a clean bit of cloth - this combined with new pads, toe the pads in slightly and make sure the cables and housings are stainless steel, the housing isn’t too flexy and what the others have said about the straddle cable adjustment - should be able to make braking very good.