I would start flushing immediately with just water. You're using inorganic ferts that need a couple of weeks to flush. Change the water ever few days if you can too.
It's 8 weeks from when you first notice budding. It takes a little while after switching to 12/12, as much as a week or two. Pistils on my current ladies started popping up within 5 days after I changed the photoperiod.
Good deal. Sounds like everything should go smoothly. Did I understand you correctly, you have the ballast mounted inside the cab? That thing doesn't get hot?
I have some Afghan going right now and I can't say it's well-suited for hot climates. Growth was a little stunted during veg due to heat and I finally had to break down and buy a Cool Tube for flowering. My last grow had major heat issues and the Master Kush I had going then came out ok despite...
2x600w should suffice. Cool Tube reflectors would be good too. You can easily connect them to your fan, but you'll need an 8" to 6" fitting because the Cool Tube has 6" ports.