Interestingly the best time to go out is at solar noon, when the UVB/UVA ratio is higher. Just go for a shorter amount of time to compensate for the higher overall intensity.
I agree, but you can titrate your exposure. So at the beginning of the season, in the 12-3 window you can start by going 5 mins without sunscreen for a few days, then 10 mins, then 20 etc. depending on your skin type.
The worst thing to do is to go from low exposure (i.e. winter months, or just constant indoor time) to long periods of exposure, even with sunscreen.
No, UVA is stronger and more harmful. UVA penetrates deeper in the skin, since it's stronger. UVB stimulates Vitamin D production, while UVA doesn't.
So almost anything that is "UV-blocking" (sunscreen, UV-treated glass) gets rid of all of the beneficial UVB before UVA starts getting reduced. So you are actually enriching your exposure to the most harmful UV type, and not making Vitamin D.
This might explain the paradoxical finding that people who use sunscreen more can have higher rates of skin cancer