The proxy you are using seems like a good one and if you are using auth on it you aren’t exposing the services under it directly, so the vulnerability would be proxy or your password to reach any potential vulnerabilities on the service. Sure there could be some crazy bad vulnerability on the proxy, but as long as your using a good trusted one and not doing some config to bypass their security, and updating it, you should be fine. Some people here think you could use vpns and such for everything and sometimes you just gotta share your services and going through a proxy service is a good solution.