Don't strip it, this is almost certainly fixable. What happened is the varnish frosted on you, and the hardware store rattle can is a big part of why. Those are usually much coarser formulations meant for wood or metal, and they go on thick, which dries cloudy over smooth blends. Humidity does the same thing even with a good varnish, so if you sprayed on a damp day or in a cold garage, that alone can fog a model. I frosted an entire warband once by spraying in the evening when the temperature dropped, so I feel this one in my bones. Here's why the gloss first then matte thing is real advice and not a myth. Matte varnish gets its flat look from tiny particles sitting in the dried film, and those particles scatter light, which kills the depth in your blends and makes the face look flat. Gloss does the opposite, it dries clear and actually restores the saturation and contrast underneath. So a gloss coat can pull your chest and arm shading back to life, not bury it. What I'd do: grab a hobby gloss varnish, brush it on in one or two thin coats over the worst areas, the chest, arms, and that skull on the base. Gloss fills recesses a bit but a couple of light brushed coats won't clog fine detail the way you're imagining, especially if you wick excess out of deep crevices with a damp brush. Once it's dry, the blends should look like they did before varnishing, maybe even better. Then, if you still want the flat finish, go over it with a proper hobby matte in very light passes, holding the can further back and moving constantly. Two misty passes beat one wet one every time.
Test the whole process on the base skull first since it's a small area, and you'll see the recovery before committing to the rest. Also warm the can in your hands and shake it way longer than feels necessary, and spray somewhere with decent airflow and moderate humidity. Your paint job is still under that film, it just needs the right topcoat to come back.