Your assessment of the damage is correct for the most part except that later on you'll be able to change enchantments yourself, which in the end makes most of those yellow named weapons better because they tend to have more enchantment slots than random weapons. For example, a named weapon with no enchantments will probably do less damage than a green with a damage enchantment, but when you're able to put the same damage enchant on the named one it will be much better because it will more than likely have other slots to put even more enchants (like crit chance, etc) and it'll probably have more charm slots as well.
About speed, from what I've seen, it just changes between the weapon setup you have, not between weapons themselves. So for example 2h is slower than dw but one 2h sword won't be any faster or slower than another.
And dual wield does hit with both weapons except that the offhand weapon gets a rather large negative damage penalty unless you invest points in dw spec, which is well worth it since with enough points the penalty changes into an equally large damage boost later on. On the other hand, 2h weapons have higher base damage and don't get a penalty for not investing points, but since it's not my preference I'm not sure if it gets as high a damage bonus as dw does.
