For your first question, check the CAA website (link below). The bit you're interested in is probably 'anisometropia'. You'll find that many of the medical requirements are qualified with 'a fit assessment may be considered...' In other words, falling outside the requirements is often not an automatic no-go: they will just require a specialist's report before considering issuing you with a medical. If in doubt, call them and have a chat. They are generally helpful.
With regard to your second question: 'cargo pilots' are subject to exactly the same licencing requirements as those flying passengers. Further, you won't be working for FEDEX or UPS without a green card or US passport!
Visual System GM | Medical | Personal Licences and Training