DanPascal:
What do you mean by application notes?
Documents written by the manufacturer about how to use their product. Bosch very likely has application notes related to the BME280 (and related BMP280 and BMP180) giving you suggestions on how to use them.
Measuring the pressure of a moving fluid such as air is VERY difficult. No surprise you get great results in static air, but noisy values all over the place when it's moving.
The moment you have air flow over the end of a tube (tube vertical, air flow horizontal) the pressure inside the tube drops, even if the pressure outside doesn't change at all. Change the orientation of that tube in the same air flow and same air pressure, and the pressure inside the tube changes.
Now look at your BMP280, you will see this tiny hole. That's similar to this tube. So when air flows over the sensor the pressure it measures depends on how it's oriented in the flow. Very likely your flow is turbulent as well, and that will give a lot of noise in the readings. You mentioned 3D printing the parts, so the walls will be rough adding more turbulence.
For any chance of accurate readings you have to talk to people that are specialised in wind tunnels, pressure measurements, etc. They will at least be able to tell you what the problems are and ways to overcome them. Not much chance to find those folk on this forum... I also only know just enough to know it's not exactly straightforward.