Bleeding episodes at 5w6d, fetal heartbeat visible but too weak to measure (60-80 by ob est), ccs normal embryo, high nk/tnfa. Chance to sustain preg?

Yes. The heartbeat varies by week of pregnancy. Sometimes at that time you may not even see a heartbeat. But it is fine if the heartbeat is low. But in a week it should rise and hopefully everything will grow well!