Best waf setup for Prometheus and Grafana

Hello together,
I am a Cloudflare Pro customer since yesterday and I really really like it. I am using Grafana and Prometheus behind Cloudflare (Prometheus with a access policy). After enabling the waf all requests to the Grafana API endpoint /api/datasources/proxy/ started to be blocked. And the Prometheus queries that Grafana does started to be blocked too. Do you have any tips on how to best setup the WAF for these two web apps? Or should I just use rules to disable to waf for example /api/datasources/proxy/*?

Oh and also why is it not possible to disable certain WAF rules using page rules?

Thanks for your help.