Whoa easy here. lol
Dont make this too hard, its not that complicated.

Find a good number of bubbles per second that keeps your co2 at a level thats ok for your fish. Any co2 you add will help your plants anyway. Start with two lights on and low co2. Then let the tank stabilize with that. You will have algae until it does this, dont worry it will fix itself as long as you dont mess with it constantly. The algae will just start disappearing when its overcome by the plants. (plants grow roots first then growth starts after that) Remember to do twice a week 25% water changes to help with mineral balance.
The size of your tank is fine with the current that would be provided by a properly sized canister filter. You would not need any extra water movement at all. The co2 will diffuse just fine throughout the tank. Id kill for a lily output if I could afford it.
Second if you want to see the flow in your tank drop some flake food in and see where it ends up, I bet all over the tank, and the co2 spreads way easier than that.
If your ph bounces around and your co2 levels wont stay constant then your kh might not be high enough and co2 might be out of the question without some costlier products.
If you are using HC for a carpet plant you need to break it into very small clumps and place it all over the bottom carefully. It will take time to spread and may look like its dying back at first, leave it!