@joshuao sorry for the late response but glad you got something working. frp is an excellent project and highly recommend it for anyone looking for a production-quality solution.
For reference, in your boringproxy example you would need to specify the port when running the client ssh command, ie
ssh -p 8000 root@ssh.mydomain.com
You also don’t need to open any ports on the client, but you do need port 8000 open on the server. Also, Server HTTPS is definitely the TLS termination option you want.