you are good. The hairline cracks are totally normal and they do not cause the finish to come off during cleaning. The soot ring sounds like the dome needs to be adjusted because that means that smoke is coming out of the gasket. You don't need a gasket to run an egg but you need to adjust the dome so it's flush on the base no matter how you run it. There are many videos out there but I'll link you up to one if you think this is an issue. It could have been done already and the soot is residue from before.
Good news is that BGE will cover any defect in the porcelain (assuming he is the original owner and bought from a legit dealer) so if it actually gets worse or affects the performance in any way, they will take care of it.
There are really no issues other than cosmetic so you didn't break anything. You just made it a little uglier.