Attend an Aish HaTorah Discovery Seminar. Start learning Torah. Find out what is unique about Judaism and why Jews for thousands of years would rather die a martyred death than convert, yet marry out of Judaism. Likewise, the non-Jewish intendee should investigate his own heritage. If you won't make a decision to make a complete separation and stop communicating, then make a pact with each other to have no physical contact for three months.
Life is tough.
A marriage should be a partnership to work together, grow and to weather the tough times. Marriages are so fragile these days anyway, that is truly unfortunate for a person to consider a relationship with built-in problems of such magnitude.