A lot has already been said, so I'll try to be concise here.
2. Meals and beverages are not a consideration for me when I take my pm dosage. I'm not aware of anyone reporting of this making a difference.
3. No, I don't think 12 hours is too far apart between doses. For a decent portion of my pm regime, I took my pm capsules twice a day and that didn't seem to impair development. If you're having trouble with development, it's certainly worthwhile I think to keep a steady supply of pm in your body to see if that helps make a difference.
4. I take 800 mg of spearmint and that's enough to make a difference for me. As CK mentioned, you may need to give it more time.
5. Did you buy a different brand of PABA from Swanson? The ones I got are 500 mg per capsule.