Jose,
Obviously your tank isn't cycled, and has not made any progress for the last 2 months. This suggests 2 problems: what killed the bacteria in the first place and what is supressing regrowth for the last 8 weeks. This presumes that your nitrite and nitrate tests are working as well as your TAN test which you confirmed. Nitrite is hard to confirm unless you have a reference solution but you can confirm your nitrate values by testing your other tanks. If they all read 0 time for a new test.
How many tanks are you running?
Did you possibly forget to turn the filters off overnight after a water change before this started ?
Any recent medications?
How long was the tank cycled previously?
What is your filter changing/cleaning routine? Do you possibly clean with tap water?
A level of TAN of 1.0 is (at a ph of 6.8 and temp of 80.6) non-toxic. In fact you are safe at this pH/temp up to ~ 4.0. Regardless I would be changing the water daily or every other day to keep your ammonia well below that until you (re) cycle this tank. At the same time to be safe I would drop the pH to 6.6 and the temp to 78-80. Neither of those changes should excessively stress the fish.
I would not start changing filter media just yet unless this tank was never cycled. Unless you are concerned in re CC I would first gently clean your 3 filters contents in tank water, then innoculate all 3 of your filters with material from a cycled tank filter. You should start seeing a drop in ammonia and a spike in nitrites within a few days. Your particular bottle of stability seems to be dead. Are you possibly also using a UV filter? That would certainly inhibit the bacteria in stability. If you do not want to use filter media from another tank, you can try a new bottle of stability or a different product, and if you have a UV turn it off for a couple of days after adding.