The ammonia tester can be very tricky. Some people do find it impossible to tell the difference between the 1 and 0.25 colours. It is not uncommon for people to have had tanks for years, full of healthy fish with an ammonia of 0.25, which is put down to the problems reading the tester.
Nitrite is different; it is usually very easy to tell that zero sky blue from even a hint of purple below 0.25.
Does nitrite ever drop to zero, and how long after adding the ammonia? If it is over 1ppm when you test, don't add 2ppm ammonia, just add 1ppm - but that is only when you also have zero ammonia twice, two days apart. Adding too much ammonia, even though nitrite is not going off the top of the scale, might be leading to too much nitrate which can also have a detrimental effect on the bacteria, coupled with the falling pH. These bacteria like high pH to multiply.
Thinking about it, remove the wood till the cycle finishes. If you can bear the thought, empty as much water as possible from the tank, refill it with warm water adding bicarb as you do so, then add 3ppm ammonia. This won't harm the bacteria you have already grown, they are nice and safe inside the filter (and on everything else in the tank) but it will reset the water back to low nitrate and high bicarb. Then test in 2 days, and again in another 2 days. If you have 2 zero ammonias, go by the nitrite readings.
If nitrite is over 1ppm at the same time as the second zero ammonia, add 1ppm ammonia; if nitrite is below 1 at that reading, add 3ppm.
I have 0.5ppm ammonia and 5+ppm nitrite today for the first time. It is day 28.