Comments from one DIYer to another -

Option one seems best to me unless there is serious settling that is continuing.

Our garage slab had moved away from the driveway a bit and the gap was home to ants and weeds. I put foam backer rod into the opening (available at your average home store, usually used in large gaps around windows and such before caulking) then squirted in masonry caulk (also available at your neighborhood hardware store). It has held up very well.

Our house is doing the same thing - our neighbor suggested having a towing company (like big enough to two a semi??), come in and jack it up and then put supports (like jacks) under it. I called a towing company and asked to have them come out and see if it would work, but no one ever did. May risk it breaking - ours is half-circle shaped. That's just another idea for you. At this point, I've just chosen to ignore ours until other more pressing things are repaired, remodeled. Never gave the basement wall being damaged a thought before, but now I'm concerned.

I believe our situation was similar. We have a concrete porch at the front door which has a foundation projecting about 6 feet into the lawn. Then a concrete step down to the sidewalk. The step and first section of the sidewalk were settling. I believe this is a consequence of backfill from construction.

I had a concrete jacking company lift it. They drilled a hole through both the step and sidewalk section. Then, under high pressure pumped concrete into the void below thus lifting everything level. It cost $275 but I'm not sure I would have been able to lift and level it myself. Aside from a newer concrete "spot" on the surface one would never know anything was done.

I sold a house for a client a few years back and the stairs (7 high) were pulling away at about 3 inches. Enough to get a small child's foot caught for sure. There was a company that came to reset them. It cost about $600. The reason was that they were huge and heavy, surrounded by shrubs, and did I mention huge and heavy? Even hollow steps (which these were) are extremely heavy and dangerous to mess with, so even if you could jack them up, you would never be able to reset them properly.

I would either caulk them, or use some thinset mortar and some nice patio stone to cover the top treead area, and cover that gap. Good Luck.

Can someone recommend a conpany that would do this in virginia, fairfax area