What direction do the windows face now?

Easy question for the builder. They may have additional plan sets that already have the structural calculations and verification done. The engineer/builder should be able to tell you in a jiffy.

Yes, yes and yes!

Definitely put another window on the north wall in bedroom 3. The one room in my house with a north facing window is always a lot darker than the other rooms. Place it on the opposite end of the wall so you can place a bed between the two windows.

In bedroom 2, you could place another same size window on the adjacent north wall next to the existing window. You will have a nice bright and light corner.

I feel you can't have enough windows and light.

My son's room is just like Bedroom 2. He has the same window in that corner, and two double-ganged windows in the middle of the adjacent wall. Plenty of light, but hard to place furniture. When he was little the bed fit nicely under the windows (lots of trees so it was like being in a treehouse) but when he needed a desk he wanted it by the windows for light. So his bed ended up on the wall across from the door. It feels like he doesn't have much privacy that way.

So I'd suggest either a second window on the same wall as the existing one, but at the other end of the wall kind of opposite the door (but not too much in the corner) or adjacent to the closet. That will give you the most flexibility for furniture,