Regular soap should be fine. It's best to keep the sore clean and as dry as possible to let it heal on it's own. If it looks infected after a few more days, see your doctor.

Definitely run with compression shorts to avoid chafing as well as the fabric will wick moisture away from your skin. This will feel much more comfortable and help prevent skin irritations, boils, painful cysts etc. If you get a boil or a cyst, let your doctor deal with it or you can risk a serious infection.

If your saddle's been comfy so far, I'd wait until that pimple has healed because the fit may be fine. Your skin is just a bit sensitive at the moment and once you've healed up the saddle may need re adjusting again.

I've used Bodyglide and it is pretty thin and I have to reapply during long bike rides. I haven't tried Assos or chamois cream but have heard they help a lot. You may want to give them a try.