Hi, I thought I would pop in and add my 2 cents here. First let me tell you that when I was a kid my dad put in a sunken patio. It was 18" below grade and he put down sand and then layed in brick. We had very heavy clay soil so it was thought that settling wouldn't be much of an issue. After a few years the bricks had settled here and there, with standing water after steady rains pooled in the low spots and took quite a while to drain off resulting in some areas accumulating moss. A little slick to walk on and a bit of a hazard after a long time. The bricks were also no longer tightly layed next to each other either. After less than 10 years he ended up laying a piece of outdoor carpet over the bricks to hide the unsightly moss and reduce the chance of slipping. Even with scrubbing the moss regularly with bleach to remove it he ended up losing the battle. My husband (a bricklayer by trade) put a new patio in at our home and used a limestone screen base. It has been 2 years and there is no settling at this point. Weeds are at a minimum. Occasionally we will have a few pop up but they have been very easy to pull. We used large irregular sized pieces of sandstone for the patio that were reclaimed old sidewalk squares that we decided to break and make into an asymetrical pattern with a brick spiral in the center. So far so good with the crushed limestone base. Excellent drainage, no standing water even after heavy rains. we did install a french drain below the crushed stone to promote even better drainage as well though.

All three. The topsoil will hold the base material in place, you will still need to edge the walkway but the soil will hold whatever this is in place too. You could do it the other way round but this would involve concrete to hold up the edgers and this is the way most commercial jobs are done. Topsoil first is the cheapest way.

The only time you would utilize CA-7 is in a permeable base situation. CA-6 (grade 8) is the preferred gravel for patio and driveway bases. Then 1" of torpedo sand or CA-16 chips as a bedding course is added on top before installing the brick. Any compaction should be done in 2" lifts unless you have an exceptionally large compactor. We are also in the Chicago area and that would be our standard operating procedure. Good luck with your project.

I don't see a way to edit my original post, so here's an update: I dug out along the border of the walkway tonight in a small area. It looks like the bed of cement for the edge pavers goes down 2 or so inches, and when I pried against them, they felt pretty securely in place. It seems that adding an edge restraint would be pretty difficult with the concrete bed extending beyond the walkway's edge, but hopefully not necessary anyway.