yeah, you are close on the CO2, but you really want to consistently stay about 25-30 ppm to help you curb any kind of algae growth. You could add another bottle to your DIY system, or decrease the interval between mixture changes.
As far as ferts, there a few different methods.
First off, you need to have the correct fertilizers on hand. Chelated iron is important, but you also need to be worried about your macroelements... Nitrogen, Phosphorus, and Potassium. These are available in several different forms. The most economical is to buy dry ferts, and mix your own solutions. However, I am currently using the flourish line of N, P, and K (three separate bottles of fert). On top of that, I use another fert called leafzone, which contains Fe and more K. I also use a comprehensive formula from flourish that contains the essential trace elements. Now, how much do you add? Well there are a few methods for this as well. One popular method is the estimative index, or EI method. This basically involves adding more than required to the tank, and then doing a large (50% or more) water change at the end of the week to sort of reset the clock, and the process starts over. Search for Estimative Index in google or on the forum, and you will find a plethora of information on this method.
The method I use, is basically I test for N and P, and aim for specific levels. K (potassium) I just add rather liberally, as it is hard to reach a lethal level of K. I then watch for defficiencies in my plants, and adjust the dosing regiment accordingly. There are
several places to find "symptoms" for defficienies of various elements. I don't thinkthe dosing has to be an exact science, as long as you don't add lethal levels of any 1 solution, or allow any 1 macro to bottom out. The periodic testing (usually weekly or so) just kind of keeps me on track... I may add some extra N here, or P there just to keep levels as close to my targets as possible based on the tests.
With this method, I generally dose everything about twice a week, and just perform regular 10-15% water changes on a weekly basis. Seems easier than the EI method to me, but I am not speaking from experience, as I have never attempted EI. The prospect of a 50% water change every week for my setup seems daunting.
OH yes, I and I would strongly recommend a timer for your lighting. Establishing a strict photoperiod for your tank will make it healthier for fish and plants. You can get 1 for cheap at radioshack or online.