From the looks of the picture you picked the stitches up right. No, you don't pick up stitches across the bottom, the garter is going parallel to the sides. Are there any instructions about sewing the edges right above where the bottom center flower is, to join the two sides? From the way the picture looks it seems that that may (see below) be needed because you are not knitting in the round even though you use circular needles.
The knitting f/b at the marker placements would be what causes the increase to create the roundness at the top inside edge of the neck.
To get garter stitch you need to knit every row. Don't purl any or you will get stockinette.
When I first read though it I thought maybe you were suppose to knit in the round, but from looking at the picture and the direction of the garter stitch that is not what is happening here. When you have completed the 7 rows (back and forth) of garter stitch, you may sew a few stitches right at the center front to join the two sides of the neck trim, but they may not sew it but just let them come together and not sew it. Doing the 7 rows from one front edge to the other is what fills in the space and makes the center edges come together. So when you quit before you had 7 rows you would not have built up enough rows to fill in the gap. If I'm right about this, it seems you would need to catch (sew) the edges of the garter stitch down to the space where you were wondering if you need to pick up stitches there in the front. That straight line right at the bottom of the neck. This would be the last step.
So you pick up stitches along both sides of the "key hole" from the right front back around to the other front, work 7 rows back and forth of knitting every row (garter stitch) and then sew the edges down to the flat line across the center front to finish the whole edge. And maybe add a couple stitches right in the front to join it right in the middle, or not, as desired.
That's what I think. I hope this helps you figure this out. Merigold