Those really are darling stockings.
There are two things you might try:
Count the slip sts at the edge of the heel and space out your 5 picked up sts, skipping some of the slipped sts.
Pick up an extra stitch or two along the side of the heel so that no rows are skipped. Pick up an extra stitch at the corner where the heel meets the upper part of the sock. You can always do an extra row or two to decrease sts, just make both portions of the heel the same. The extra stitch at the corner can be decreased right away as Amy does here.