CO2 isn't going to kill algae. The DIY CO2 sure ins't helping, it's not nearly as stable as injected CO2, and fluctuations in CO2 will favor algae growth. Stable CO2 favors plant growth, but if your tank is out of balance CO2 will make things worse. Not to mention swings in CO2 when you are trying to find the right amount that will work for your tank
Hydrogen peroxide may work but it is a toxin. No idea how it will affect your fish/plants/bio filter. Staghorn algae is a food source for lots of fish, like rosy barbs, Florida fag fish and many others. Just remember depending on your stocking adding a new fish my not be the best idea.
What type of lights do you have? And how deep is your tank? My thought is that you have too much light. IF they are T8 remove 1 bulb T5 remove 2, depending on depth. Also, limit the light no more than 8hours per day.
Edit: flow is always good in a planted tank. Helps deliver nutrients to the plants. This fluctuating CO2 business is the reason I swear by low light/low tech heavily planted tank, letting your fish produce CO2, and maintaining some surface movement is a fail safe way to keep steady CO2 levels.