I see that Zpool uses Cloudflare but the API response is not cached. I think you could easily cache it for 1 minute as I don't think it's that crucial to have realtime data (1 minute is close to realtime anyways). I know that in Cloudflare the shortest time for Edge cache TTL is 2 hours but you have the option "Respect existing headers" so on the server you could have 1 minute set.

Also, I just got an Error 524 timeout error so I guess the web server is not able to handle the amount of traffic it gets. You should enable caching dynamic content on Cloudflare as you don't have user generated real time content. On Cloudflare it's under Page Rules, you set a rule for *.zpool.com/* and set Cache Level to Cache Everything so it will cache your html content as well and your php processes won't die or you won't run out of cpu or memory.

You might run into some issues however with the Wallet subpage as "http://www.zpool.ca/?address=" will be served to everybody with the same content so you might have to remove the address history or any other content which doesn't have unique URL.