If you go to the US website and ask for availability, you will be contacted via text from someone in the US store when one arrives there. That's what happened to me at least. They were OOS on the CoolBox MM in black so I asked to be notified. Got a text from a NYC SA and in about a week the bag was in my hands. It was shipped directly from the NYC store by that SA.1-Ask customer service about where order fulfillment takes place, and specifically ask about duties. IMO your bag order will be fulfilled from Europe, unless you contact the NYC boutique directly.
2-The weight of the bag is a function of size and type of leather. A box calf MM will weigh more than a crispy calf MM, for example. Again, ask customer service about the weight of the bag in your specifications.
Always good to remember that high-end luxury customer service is usually top-notch - you can ask anything about the product. Delvaux offers personal stylist service, and they can answer questions about size, weight, coloours, etc.
Good luck in your decision!