Hi there, Hawk21M-
Are you doing your B737 type rating or what?
Anyway, I have only flown the B737-200, so I can't aswer all of your questions on the NG, however, I can help you with this one, I think.
In aviation the aim is to keep things simple if you can, so unlike for the #1 and #2 windows, there is indeed no heating element in #3 windows, because even if it would have ice on it, you don't need to look through this side window to fly the plane anyway.
Ok, but I have never seen ice on the #3 window, although it is unheated! How can that be?
Well: in order to prevent ice from building, they have made this window from a different material, which is less likely to encounter icing then the glass windows, thanks to its improved ability to transfer heat from the cockpit. Sadly, this material has not the same strength as glass windows, for instance in case of bird strikes, which prevents it from being used in the other windows. However, ad a birdstrike will always be a frontal strike, never a sideways strike, this is no problem for the #3 window.
I don't think you'll find this explanation anywhere in the manual; it's just something I have come up with myself, but I think it is quite a good one...
Any other ideas, guys (and girls)?