CO2 isn't an anti BBA agent. You need to kill it or remove it. CO2 is for healthy plants and healthy plants usually reign in algae.
As for the ppm question, you can use the drop checker to give you a visual indication if you have 30ppm. Most experienced plant keepers can just look at the plants and fish to guess how much CO2 they have.
ps. CO2 in air is measured in ppm by volume and in water it is measured in ppm by weight.
bubbles per minute are just a bubble count of how much CO2 your set up is offering to the water.
It is another question as to how much of those bubbles are actually getting dissolved into the water. That is where ppm comes in.
Yes, make sure you're dissolving the CO2 into the water. Some sort of diffusion device is used for that and ppm quantifies how many molecule of the stuff is in the water.
There are several methods to kill BBA
1. use Hydrogen Peroxide. Don't use more than 2ml/Gallon of it in the water. It can kill fish an plants.
2. use excel or something equivalent in Europe. It's the carbon supplement whose main ingredient is Glutaraldehyde. Double the dosage. In addition to being a supplement, it also is an excellent algaecide. Again, it could kill fish and plants if overused.