You need to be having this conversation on a forum specialising in hosting etc. You are self hosting.
This has almost nothing to do with CW (Calibre Web) and the CW has little to do with Calibre support here as it's just using the calibre files.
Also you need a dynamic DNS service as the public IP will change often and because it's cellular/mobile may only activate when your home system connects to the network.
How to see is there NAT in T-Mobile's network?
Use your browser on any site that reports the public IP, like this one:
https://www.grc.com/x/ne.dll?bh0bkyd2
Use
https://www.grc.com and find "ShieldsUP!" on their website if direct link doesn't fail.
Now see has your Router got stats on IP address. If it's not the same, then there is a NAT on T-Mobile and you can't share to the internet, you'd need hosting and rsync.
You can't use traceroute as it only lists complete routers, not NAT, and usually doesn't show your home public IP but the LAN IP.
My Internet connection on the router statistics is the same as GRC, so there is no NAT. There almost always is on Mobile/Cell, which is what 5G is. Three in Ireland certainly uses NAT.