That thick gasket you installed should absorb a quarter inch surface difference . You got some serious warpage somewhere.I wonder if the three 'burn' areas (2 center; 1 to the right) are from coals falling on gasket. Not sure about the stains.
You mentioned that it does not compress very much and that is about 1/8" thick. I see the 'ledge' on the left side where the stove gasket runs vertical. I wonder if air passes thru there.
I have some stuff similar to what EbS-P mentioned in post #11 above. It is a woven fabric that will mold better to the door gasket. I had used it for a window seal. It has adhesive on the back. I may run a strip of it across the bottom as you did. But that is dependent on what I hear back from SBI and there quality group. No word yet.
Do you know how to site one surface edge on a door to the opposite edge?....if not get a carpenter buddy to look at that door and site across from one edge to the other. A good carpenter can see a 1/32" warp in anything if it exists just by looking at it....A machinist as well..