So, the first burn off didn't accomplish much. The gunk on ALL the surfaces is measurable, literally was scraping off chunks. I got frustrated and piled the basket high with charcoal this morning and let her rip. White smoke billowing red hot coals, I didn't check the heat because I knew it would stress me out. Hours later and the dome is actually clean! The bottom that was behind the box and ring is still black but there is no more thick stuck on mess.
I am seasoning the grate. I had no choice but to clean it to scratch. The spaces in between the ribs were barely open because they were filled in with who knows how many dinners. Yuck!
Thank you all for the help with this.
What would I use on a hairline crack to keep it from growing?