You really should go to YouTube to see how your caliper body is connected to the caliper bracket. The slider pins that you are talking about don’t have any external threads. They are what slide. The caliper is bolted to them (by internal threaded hole in end of slider). I’m guessing that you have run into this small caliper-to-slider bolt being frozen. You may also have a frozen slider. It slides into a blind hole in the caliper bracket and is sealed from the elements by the rubber boot. Ideally, this slider moves free and easy. You can test that by prying in between your pads and the rotor and watching if the caliper body moves back and forth. If it doesn’t, your slider may well be frozen also. I’ve never seen a bolt that mounts a caliper to a slider that had a “pinhead”. (Make sure that you are on the right bolt head.) When you talk about the “end of the slider bolt maybe being threaded on the end that is facing you but inside the caliper,” you are not picturing it correctly. Again, there are no threads on the slider (except internally, where the caliper bolt connects the caliper to the slider). Go online for an exploded view of your setup. Always wear safety glasses and never take sh*t from an inanimate object.