What, if anything, can I do to recover bitcoin that was stolen from my MtGox acct in June, 2013?
There is nothing that can be done with just a public address and an IP(as the real IP is most likely behind proxy/vpn/etc...).

Kraken was selected by the MtGox trustee to assist MtGox creditors in investigating missing Bitcoin, filing claims, and distributing remaining assets.
The due date for accepting MtGox creditor claims via online submission has past.
But creditors may still be able to submit claims via the offline claims method.