I saw a post of yours from a few days ago and saw that no one has responded to the curtain portion of your post. I'll try and maybe help you.
Mold and mildew need 1) moisture, 2) little to no sun but some warmtn, and 3) no air movement. If you can eliminate or significantly all or some of these conditions, your problem may go away. If moisture is forming on the inside panels, then the house is humid in that area, and when it cools, the moisture condenses on the windows. If you have plants in the window, that could be the source of your moisture. The other source is the house is too humid. If you have a humidifier in your heating system, lower it to 30-40%, or even 25%.
If you don't have plants in the window and the humidity level is below 40%, consider moving the air around. If you have a ceiling fan in the room, a low or medium setting at the most should get the air moving. The most costly suggestion I have is having an awning put up outside over the window. Yes, this will keep all that sun out but I will keep the room at a lower temperature during the day, thus, preventing the air from holding a lot of moisture. (Again, with a lot of water in a very warm room, when the room eventually cools, the moisture/condensation is squeezed out of it and it has to settle on 'things', ie., your curtains. Your curtains are acting somewhat like an awning except it's INSIDE the house. So, that's where the moisture is going to settle (on them and what's between them and the 'outside'.)
We have a south-facing bay window but we have an 8' high porch that extends about 5' out. So, we don't have your problem. We only get mid-winter sun but no moisture. The front of the house is still the warmest part of the house! There are no trees out front and we're on a hill, totally exposed. (It's a great snow melter for the driveway and steps!) If you have more infor to offer, post up. My best to ya and hope this helps.