Well first off.. Bravo! Well done with the research. You have been busy browsing the forums. You are indeed off to a great start.
The cloudy water will clear up on it's own, give it a few more days. It's just a bacteria bloom as your aquarium sorts itself out, harmless.
As for water changes, just go with tap. Unless your tap is remarkably hard and you are wanting to keep soft water species there is no need to deal with the hassle of RO. Danios are really hardy and can live in anything.
Tetra FloraPride, I'm not familiar with this product, but it claims to be "an iron intensive fertilizer with potassium and other minerals, does not contain phosphates". Well it seems simple and if it's working for you and continues to do so then thats fine. Learning very basic EI (estimative index dosing strategy) wouldn't hurt though. In the long run it's going to save you money and knowing the specifics of how your planted tank runs is a real benefit. Asking some of the EI vets about a stripped down EI plan for your tank would be a good idea.
Another option is dosing Seachem Flourish. It will give your plants the traces they need, and it does contain some nitrogen, phosphorous & potassium. I think you could achieve a balance with Flourish by adjusting your photoperiod as needed. As for the Trace, I haven't read anything proving the traces it contains specifically helps plants grow, but many people use it myself included. It's up to you again, surely wont hurt, perhaps help. Not crucial.
Carbon in the filter is debatable. It does absorb some of your ferts, but your plants are burning them up anyhow. On the pro side it does polish the water nicely. It's up to you really, I don't really see a use for it. Your cloudy water will persist for a bit with or without it.
Marsilea minuta is a really nice low light ground cover plant, happens to be one of my favorites. Theres actually a thread that recently started up in the low tech section regarding ground cover plants.
You substrate is fine. Many planted tanks, even high tech are grown very well in gravel/coarse sand. No need to tab it. Dosing the water column will suffice.
Stick with excel for the time being. If algae starts getting stubborn or you notice plants showing signs for CO2 deficiency ( stunted growth, gnarled malformed leaves et cetera) you could do a DIY CO2. It's a moderate pain changing the yeast but it's cheap, and CO2 is key to planted tanks. Shortening the photoperiod, perhaps just one of your lights most of the day, and a midday burst with both, and dosing excel, this should be avoidable.
Well thats all I have, I went the high tech route so I'm limited in the advice I can lend. I'm sure some low techies out there will chime in. Best of luck, but I don't think you'll be needing it!
I was thinking you were after a low tech low hassle planted tank.. so hopefully I answered some of your questions without giving any erroneous information regarding your goals.