Can I harvest confidently in couple days?
I reckon …Yes 
Exciting!!
What strain and how long in flower?
Do you have a jewelers loop, microscope, or macro on your phone for a close up of the trichomes?
Mine don’t, I feed till harvest and never get any “fade”.
WW about 7 weeks
Id say another week would probably do her some good.
It’s way better to go over then under as hard as it us sometimes 
If you can get a good look at the trichomes on the bits that the hairs are actually sticking out of, not the trichomes on the leafs but the little bud bits.
You want them to be milky or cloudy and not clear.
Milky/cloudy looks like plastic, clear looks like glass.
The later stage is a amber to brown color.
If most all are cloudy with a few amber then shes “in the window” so to say.
I like a heavy bit of amber so I let mine go a few days even after i think its ready
That’s probably the most asked question and really the hardest one to answer. Here’s a pic or you can search trichome color. I guess it’s all about personal preference. The loupe is a really useful tool @The_Cannabowlist and all the others he mentioned.
I’d wait at least a week, maybe 2.
Looking at the plant, I think you’re right at the start of the window for harvesting. If you had to harvest, pistols are brown and receding, and this used to be the measure for when to harvest. The longer you let it go, the more it will bulk up. To me the plants still looks a little light.
I had a blue dream Auto that was all cloudy at 5 weeks of flower, and let it go another 2 weeks and it doubled in Mass.
Gorgeous. Great work!