lighting - you are going to find that with 15-20watts of normal output fluorescent lighting you will *maybe* be able to keep plants alive, let alone grow them. I have 2x15watt 18" strips over a 10gal, and it is just enough to grow even the lowest light plants.
filter - that choice is a good one in my opinion, but it's a horrible one if you some day want to inject gaseous co2 (sugar/yeast method or pressurized). Also, as mentioned, activated carbon/charcoal does not exactly help planted tanks, maybe hurts them by removing nutrients from the tank. I believe many of the biowheel filters have pads with carbon in them . . .
substrate - nice choice!
fish - platties are good, try to find some otoclineus cats. I found them at petsmart (unfortunately, they are the only ones carrying them). I would suggest trying some shrimp too! They are fun and add diversity.
chemicals - they are all decent, don't add salt though. I've never really found it to help. Leaf Zone is okay for plants, but doesn't contain any nitrogen or micronutrients other than iron. Feedings and water changes can take care of those. Also, find out if your water supply has chlorine/chloramine in it, and if so make sure that you have a way to get rid of it.
plants - with your current light, java fern, anubias, moss, crypts, anacharis all come to mind. Not much variety!
Keep asking questions, too!