That is "not a crack". That is cracked and sunken concrete. Top coating will not be a viable solution. If you were to remove the "triangular" sunken area and replaced it somewhat on the same level as the area outside the triangular sunken area you will have about 20+ bags 60 lb. of concrete to mix and that is a lot. If the sunken part is thicker than 4 inches you just add more and more concrete mix and more and more labor. You need to decide to spend money on a patch that will always look like a patch or go all the way, which can be costly.

Until you give the fire air it will be a smokey pit. (experience) I think the drilling of holes could be a solution. 3/4 diameter may be better. Was the installer stingy with the adhesive. You may be able to force them apart with a shim driven by a hammer. (Maybe) Do you know were the materials came from. You may be able to secure some replacements if needed.

It seems rather small and by my experience (trial and error) the fire pit will be more of a smokey pit. I say that because the air (oxygen) needed for combustion would need to come down over the edge of the metal and meet the fire at the bottom, and it won't happen easily. Perhaps some spaces or holes are drilled into the metal for air, but it doesn't look like it. And the other things about too close, etc. You could try and build a few fires to check it out. Don't worry about the base pavers cracking, they might, but a layer of sand about an inch or so think, and the natural build-up of ash should insulate them. Send your picture to your insurance agent. You many get your answer.

The door jamb should have been wider, probably a special order. I had the same problem, including the concrete porch pulling away. I was able to extend the jamb and I don't think anyone notices it. I had to chip out the concrete porch to get the new door to fit. Just so it didn't look like the porch was patched a new porch project was initiated. That was pricey but makes the house POP. The door salesman never asked any questions other than "door swing direction." If he had asked the question about jamb width I would have jumped at the chance to make it right without the "fixes". The porch material salesman was a real pro. Spent a lot of time with him and he sold me all the materials from base, new sidewalk pavers, step treads, porch slabs, cap blocks, adhesives, etc. There is so much to learn as a DIYer. Methods and materials are always changing. I wish you well with your project. I think I would use a PVC trim piece where the brick molding meets the brick. Check with the door manufacturer. You may be able to remove the brick molding and replace with a different size.

I always get off. Nothing like being stuck on an expressway with 200 other cars and trucks because some cars and trucks couldn't play nice 3 miles ahead of you. Get off the highway. Slower speeds maybe but if you get stopped you can turn around and head back. You might be able to find fuel if you need it. There may be a secondary highway paralleling the expressway that was built 50 years ago. If you are on the expressway you have only two choices when things go wrong. Sit with a whole bunch of people going nowhere or 2nd. Sit with a bunch of people going nowhere. And when was the last time you heard of a 45 car/truck pileup with multiple fatalities on a secondary highway.