Regarding the psi, 3 is quite low. I usually run it between 30-50 psi; some diffusers only operate at psi greater than 20-30.
Even after the slightest adjustment to the needle, the bubble count change is not always immediate. I lost a school of Furcata Rainbows due to an impatient adjustment.
DBT can be frustrating. I'm on the fence about ripping mine out and starting again. It is starting to lift up and I am not sure if it can be replanted. I might be able to secure it with tooth picks; IDK.
I grew DBT out in some terrariums and then tied small patches onto 1x1" stainless steel squares. I planted those and under heavy CO2, ferts, and lighting, was able to carpet my tank in 1-2 months. However, it requires frequent trimming. Otherwise, the lower growth might die off and lead to detachment (as in my case).
Not sure about the algae situation. The puffers do limit your invert selection.