Check your aims for accuracy by rechecking aim calculations. Run another control strip to verify the accuracy of your control-strip plots. Yes, to some degree. Cyan or cyan-blue whites indicate a contaminated developer. Flat colors with little image detail in the upper scale indicate possible retained silver.
Yellow whites can indicate a dirty stabilizer, a marginal wash, or a sulfurized bleach-fix.
Tannish spots on the paper indicate silver sulfide deposits from the bleach-fix and wash racks. The yellow patch is for visual troubleshooting of retained silver. Visually compare the yellow patch on your processed strips to the yellow patch on the reference strip. No, as long as your process is in control. The recommended developer time is 45 seconds and bleach-fix is 45 seconds.