I use about 50psi with a needle valve to throttle it, and one of those vertical ball style flow meters to keep flow around 3-20 L/min, depending on etch or cut, and cut speed. The air travels in a 1/4 tube to a 6” long 1/8 alum tube, which is bent so it is almost parallel to the laser beam, and centered on the dot. Getting parallel to the beam makes the air a lot more effective… digs deeper into the narrow kerf. Also getting it perfectly centered on the dot is not easy, but is important to do since with a small nozzle the flow area is tiny. I like to use an etch to aim the nozzle… look where the sparks and smoke stains go, and move the nozzle until it sprays evenly (not staining one side of the cut).
At the end of the day even with great air assist, cutting such thick hardwoods is going to take some passes and time, even with a legit $200 laser. Really diodes are best for etching, or if cutting is a low priority and lot sizes are around a few parts a week maybe… more than that and I would just invest in co2. Also $200 is the big chunk towards a $500 co2 machine.