BlueBerry, Thank you for your comment. Im Glad that I can help you out as RIU has done for me
Im going to answer the questions in the order you gave them hopefully it dose not get confusing.
1) On watering your rockwool cubes, I would pull your drip tube out of the cubes and burry them in the Hydroton right next to the cubes about half way down. I found this to work great because by this time there are a lot of roots in the bottom of your pots so there is no need to get the top of the cubes saturated.
2) Im not sure about how much water is needed during one watering, I always have my water running 24/7 and have had great success with this method. you will find that your cubes are staying a bit wet, but if you have a good airstone the roots will not drowned for being so wet. I like this method because i want the plant to use whatever nutrients it can whenever it can so i always have a fresh circulation of nutrients for the plants as well. If you keep your PPM's correct you will not have nute burn with the constant circulation.
3) If you are still thinking about just watering off and on I probably only do it 3-4 times a day, you can tweek this to whatever you want but just keep and eye on moisture levels i.e.(too wet=less feedings, too dry=do more feedings in the day).
4) Like i mentioned on answer one i would now dirrect the water on the lower part of your cubes. I also do not have a spout on the end of my tubes so they to jus run about 55 gallons an hour is flowing through my spouts
Dont worry if the tops are not getting wet you do not want the base of the stem to get rotted as i have seen in other grows.
5) Yes cover your rockwool with plastic. i just used the hydroton to cover up my cubes but if you are out of room then just cutting up trash bags will work great. you do not want any algae growing in your cubes or you might get some troubles down the road.
6) On switching out the nutes if you can, do it at the end of your day light cycle or during the lights out. I would run PH water (water that is at the correct PH) through everything for 15 min then drain and do it one more time for another 15 min. I too had troubles with my nutrients about half way through my grow (getting salt buildup on everything so i switched from my General hydroponics solution to BC series nutrients and this stuff is AWESOME I have BC grow, BC bloom, BC boost and that is it. Great stuff i highly reccomend it in your next grow. The GH nurients i dont like at all. you can see in my first page the salts builtup on my hydroton as evidence that GH is going to give people trouble. just my opinion.
your grow setup is looking great!!!!!!!!! +rep to ya. if you are still having troubles or have anymore questions feel free to ask i am more than happy to help you out---------------GROW ON