I use pub key for ssh. Is it normal practice to connect to own server through public proxy? I think with plain pass it is surely dangerous but how about RSA keys?
SSH encrypts all your communication between the client and the server. So both, password and pubkey auth are perfectly safe over a public proxy. The only thing you should verify is the fingerprint of the server. OpenSSH will do this for you after you have connected to the server once, just be sure to get the correct fingerprint when connecting initially.
BTW, it's most probably not normal practice, but nothing you should be afraid of to use a public proxy for that. I sometimes use Tor for that.