I feel your pain. I can understand how frustrating it is to have algae in your tank.
But it sounds like your plants are starving, which is why algae is taking hold.
Before dosing, first vacuum up all algae in sight. Get rid of as much of it as possible. If some leaves are too infected with algae to save, and you can't rub them off, then simply cut those off. It'll be easier for the plants to recover.
Then put in some amano shrimp, nerite snails, and a few otocinclus fish. These guys make an awesome clean up crew, and will eat most of your algae.
After you've got your tank cleaned up, then start a dosing regiment 3 times per week.
What's worked for me in the past is to have:
Po4: 1-2 PPM
No3: 5-10 PPM (although a little more doesn't seem to harm anything)
Iron: 0.5 -1 PPM
K+: 15-30 PPM
CO2: 20-30 PPM (I like to keep it closer to 30 PPM)
Once your plants start coming back and are healthy, they will emit a chemical called alleopathy (sp?, correct me someone on my spelling), that will deter algae from flourishing to some degree. But this will take a number of weeks though.
Make sure to do 50% water changes once a week though to prevent a build up of fertilizers from accumulating in the tank. This method was thought up by Tom Barr and coined the term "Estimative Index".
I'd simply paste in the URL for it, but my firewall at work blocks that website.
Go to: www.aquaticplantcentral.com
Go to the fertilzer sub forum.
At the top of the forum, is a "sticky" for post. Most helpful indeed.
In the meantime, make sure to keep the CO2 constant (don't let it run empty), make sure to keep dosing, and make sure to do 50% water changes once a week.