I am not quite sure about what the actual problem is.
The domain is properly set up and does point to Cloudflare’s proxy, however when Cloudflare attempts to connect to your server it times out as it doesnt get a response.
So far so good, the output you posted refers to the issuance of a LetsEncrypt certificate and is not necessarily linked to the problem at hand. I am not familiar with Caddy but it appears you dont want Cloudflare to connect straight to your webserver, but to that reverse proxy, which then in turn connects to the webserver. Is that right?
If it is, you should check if maybe Cloudflare can connect to your reverse proxy, but that proxy cant connect to the webserver. Generally speaking, do you really need that reverse proxy setup? It simply complicates things.
Maybe Community Tip - Fixing Error 522: Connection timed out can give you some ideas.