This chemical resistance guide might help: https://o-ring.info/en/tools/chemical-resistance-guide/ Buna = NBR. Different o-ring manufacturers use different NBR compounds, so results may wary using different maker`s same nominal rubber compound. For example FPM/Viton is more chemically resistant (less swelling, no ozone cracking), and its density is around 2x more than NBR (so less gas diffusion). But it has a worse compression set than NBR (elastic memory).
Here you can check the gland design guide (gland depth/width vs. proper o-ring cord thickness, for static use the o-ring should be compressed around 15-20%): https://o-ring.info/en/downloads/technical-handbook/