Hi Annie,
I'm sorry you're having to slay so many dragons at once. I totally understand. I have several health issues that I've put aside because I'm just so exhausted trying to work on my worst problems.
I too have tested low for Vitamin D. Back in the day when I had no idea what was wrong with me a read a book on vitamin D deficiency. I tried to find it again tonight so I could give you the title, but I couldn't (my study is a mess!). I looked on Amazon and I think it's the one that's named
UV Advantage.. That book really opened my eyes. I'm pretty skeptical but this book had a lot of very well done studies. After reading it, I went to my (completely useless) gp and asked for a blood test. When it came back very low he asked me how I knew to get tested. He didn't know anything about vitamin D deficiency.
Since reading the book I have done a complete turnaround. I was the type of mother that slathered her children religiously with sunscreen and then put little sun hats on them, bodysuits instead of little bathing suits. The whole nine yards! I was the same way with myself (well plus, I had freckles which used to drive me crazy

). Now, I encourage my kids to get some sun in the summer, just like kids used to get. I smile when I see my youngest with a little color in his skin. I worry about my eldest who doesn't like to wear shorts.
I know this is completely unscientific but I have looked into a lot of neurological diseases: myotonic dystrophy, ms, mitochondrial diseases, etc. It seems like a huge proportion of patients have very low vitamin D levels. Everybody seems to question which came first: the disease or the deficiency. Of course you're probably aware of the strong link with locations with low sun exposure and high ms rates.
Personally, I have found that taking lots of vitamin D doesn't seem to help me feel that much better, but being out in the sun definitely does. I have twice spent a week in a sunny climate, thought I was going to completely crash, and then ended up feeling pretty darn good (for me). Also, when I am able to catch an hour lying on a lounge chair in my yard in the sun it usually makes me feel much better (but living in Oregon I usually have to wait for the summer). I know it's not supposed to work like that but I swear it really does with me. The actual sun is so much better than supplements. I grew up in San Diego and sometimes I just daydream about lying on the beach and soaking up the sun's rays. Something I never would have done when I actually lived there and was sun-phobic.
Anyway, I know that's not much scientific help, but I thought I'd throw my experience out there. I think you might live somewhere that has humid heat so that might create a problem as far as getting some sun. Still, if you get a chance, try it. Mmmm, it makes me feel so good.
By the way, sitting in front of a window won't do you any good (unfortunately), you have to actually sit in the sun. And don't feel like you haven't ingested enough - it's not your fault. It's almost impossible to get enough vitamin D from food. You have to get most of it either through sunlight (yay!) or supplements. Since cave men didn't walk around with vitamin D supplements, my theory is that there is probably some middle ground as far as sun exposure goes that is healthy.
A.