turbulence is not completely random so it may be somewhat predictable in its output of the pressure sensor. and exhibit patterns.

Technically it is not random as there is a mathematical description of it in the Navier-Stokes equations, but since these are unsolvable in all but highly idealized situations, in practice it is a random phenomena.

Also let me mention that there is no perfectly random physical source as they all can be modeled by some sort of mathematical equation, so your target should be to use a source with properties for which it would be very laborious and difficult for someone to create a controlled interference in. Hence the turbulence idea.

Just attach a standing miniature fan next to your box and then place a sensor in front of it to measure its turbulence and feed that as entropy into the system (perhaps even regular pressure/velocity measurements may be suitable if an attacker can't find a way to control these props).

The input from this could be replicated by "just attach a standing miniature fan next to your box and then place a sensor in front of it to measure its turbulence".

When generating private keys of any sort, you should not try to reinvent the wheel. If you are using something as a means to generate entropy in addition to using entropy from a known secure way of generating entropy, at best, you are going to have the same amount of entropy, but you may end up with less entropy.

You either trust your computer to generate a random number or you don't. Using additional input is not going to change this trust. If you don't trust your computer to generate a random number, you should use something that you know will produce a random output, such as a coin toss or a dice roll.