I would suggest you're overdoing the exfoliant. Sounds very harsh.
1. I do not have that problem it kinda sounds like you are allergic to something in whatever product your using bump defense products works well for me
2. Do wash or clean your dome before or after the shave if not both? To rid of the dirt and oil and kill any bacteria that may be there so you have a clean head not a dirty one, thats a must.
3. I wash in shower to prep my shave and to allow the hot water and steam to soften the hairs a little for the shave. I use my cleaning product whatever I have, sometimes after my shave with a cleansing moisurizer and cold water rinse. My dome smells great when I use the moisurizer then the aftershave and what not.
4. I would suggest not using anything harsh on your scalp or anyting abressive also have you tried using sensitive shave cream/gel razors ect. or anything for sensitive skin?