First of all welcome to the forum its a great place to get any information pertaining to planted tanks you would like.
Here are some pretty basic answers to your questions is you would like me to be more specific on anything just let me know
1. We usually use bulbs that are 6000K abd up from planted tanks. I am not really that familiar with halides but i do know some use them for planted tanks and have great sucess. Most use T-5s though it and i am not sure what the rule is for bigger tanks bc i only have a 55 and a 20 but depending on what type of tank you want i think you should have enough light with just the t5s alone. For a tank that size i would think that much light would be considered on the high side of medium lighting (someone please correct me if i am wrong)
2. As for the co2 that should be fine you just need a few more things such as a solenoid which you can control when the co2 goes on and off with a timer. You will also need some co2 proof tubing, a needle valve, and a bubble counter. With what you would be using for lighting i really think you you be better off with using co2 as to avoid algae problems that you could very easily enconuter.
3. Yes i do believe people in the planted tank community use sumps i have no experience with them (i use canister filters) with a tank that size yes it would be wise to use many powerhead becasue you are going to need to have good circulation so that the co2 and your ferts get to all of your plants. You need to come up with a good circulation plan before you get your tank set up.
4. I have never used mineralized topsoil.. i use eco-complete or flourite for my substrate and have have great sucess.
5. I dont think i have ever heard of someone using 100% RO water most people do a mix, but once again i have never used it.
6. For dosing you are going to need a source of Nitrogen, Potassium, Phosphorus, Micros and Iron (if desired) here is a great sticky post to get you started on that
and here is a great place to get your ferts from