Hello,

Here is a calculator for what you need.
https://www.stego.de/nc/en/services/calculation-tools/cooling-calculation/

Just write the Temperature differential, the Installed stray power in watts, and your altitude. They will provide how many m3/h you need to cool everything down.

I can recommand to order something like this for the extraction.
http://www.ventilatie-systemen.eu/extractor-isolated-with-torin-4250-p-1413.html

They are quiet, and are very powerful.

Edit: For the humidity the best practice is 50%. High humidity = condensation, Low humidity = cause electrostatics discharge
You can use a dehumidifier if you have a condensation problem.