As the mother of 3 grown children, buy the extra seat. You have no guarantee of a bassinet even as 1Ks. It's a long flight and even in E+, you will have too much stuff to juggle and will be happier with the extra space. I would skip the bulkhead so that you can put the armrests up again for maximum flexibility. On the carseat, no answers but if your baby is happy in it and it's FAA approved, I'd try to use it.