Does measuring small during first us appt (being 1 week off - measured 6w2d, should be 7w2d) indicate issues down the line (i.e. increased risk for down syndrome or other chromosomal abnormalities, etc.)?

Conception date can be determined by Last Menstrual Period (LMP) or by early ultrasound calculation. If the dates do not match, the Ultrasound date is typically more accurate. It does not mean that the baby measured small, just that your original calculation may have been off. Because ovulation varies with each cycle, conception dates are difficult to pinpoint with LMP.