Welcome! You've got some good questions! If you post this same question in the Live Stoner Chat thread, I'm sure you will get several different answers. Growing is a personal journey/process. You have to find what works for you. To answer the one question that wont have several answers.. A good soil PH is pretty much anything in the 6's.
I don't flush autos at all so I wouldnt know what to tell you on that. Especially not at that midway point. Ive heard of people who grow photoperiod plants that flush at the half way point, right before they flip to 12/12 and bloom nutes.. But not with autos. If you just flushed out all the food and living microbes from the soil, I'd feed them asap, at the recommended dosage to get that back into the soil and roots. They need all the food they can get when flowering.
If you are growing autos, the "10 weeks" is total time from start to finish. If you are groing photoperiod plants, the "10 weeks" starts the day you flip to 12/12.
Hope that helped a little!
