You mentioned 'redirects' to https://localhost:8443. Does the URL Rewrite rule actually use a 'redirect'? If so, it's not utilizing ARR and is causing a client-side redirect to localhost, which the end users won't have access to (well, it will depend on if they have a site listening on their local computer on port 8443).
Instead of a redirect, use "Route to Server Farm", and point to a functioning server farm. That will cause it to function like a reverse proxy.
Check the health tests on the server farm to confirm that it is online and functional.
Additionally, if you're trying to use a site that is on the ARR server (i.e. localhost), then you may not need URL Rewrite or ARR. Just change your binding from 8443 to sub.example.com on port 80 and it should work directly.