Will the water permeate down to the bottom of the dry concrete?

Yes. It's a slow process but it does eventually saturate.

Yes, if you used enough water according to the mixing instructions, it will reach all of the concrete.

i used a old screw driver and stabbed several holes into the concrete when it was doing this. the water percolated down and the concrete set and held the post into my chainlink fence just fine. you could also next time add half concrete half way deep then add water then add the other half then water again. I have used both methods and it seemed perfectly fine for me.

The short answer is yes. The following is directly from Quikcrete's Data Sheet for this product: INSTALLATION FOR SETTING POSTS 1. Place post into hole and temporarily stand straight. The hole diameter should be 3 times the post diameter. The depth of the post hole should be one-half of the above ground post height. 2. Pour dry mix into the hole until it is approximately 3" - 4" (76 - 102 mm) from the top. 3. Pour water into the dry mix until the powder is saturated with water. Depending on soil conditions, this will require about 1 gallon (3.8 L) of water per 50 lb (22.7 kg) bag. For holes deeper than 2' 6" (0.8 m), place the material in lifts of 2' 6" (0.8 m) or less to allow water to soak all the way through. 4. Fill the remainder of the hole with soil dug from the hole. This product sets in 20 - 40 minutes. Wait 4 hours before placing heavy objects. The Quikcrete site has a wealth of information, including volume and material calculators, for their many great products (no, I don't work for them). - O.R.G.