1. its not to late, obviously the later you wait the less veg time the plant will have wich will result in smaller plants and less yield, would consider july to late to bother with for the yield that you would get from each plant.
2. keep with your normal veg light cycle there is no need to adjust it to the current day length.
3. the dark period that actually triggers flowering can vary from strain to strain but most will start to flower with 10-11 hours of darkness.
4. sounds fine
5. probably a good idea especially if you will not be able to visit them to water the plants very often then crystals should atleast help.
the existing soil if black loam would probably be fine and you probably wouldnt need to use another soil but admendments like manure could help out some just make sure its composted and not fresh would probably mix in 25-50 percent manure with your existing soil as long as its composted you really do not have to worry about adding to much.
horse manure is usually a little better than cow manure.
8. the only thing that I can think of would be to use it as mulch on top of the soil.