Thank you very much for your answer Dr.
Welcome to the forum.
Some questions can be answered accurately from the information in the title, without reading the question itself. That may be the case here. Trichomonas is not an oral infection and is not known to ever infect hte mouth. Transmission by oral sex is not known to occur.
Now I have read your question. Congratulations on a responsible attitude: avoiding sex for a few ideas after you and your partner were treated for trichomoas was the right thing to do. But you were exactly right: "we both believed we were supposed to stay away from penile/vaginal intercourse and not oral sex". In addition, even though the official adivce is usually to avoid contact for a week, 5 days probably is enough, even for vaginal sex.
1) Your partner cannot be infected in the oral cavity.
2) Yes, at 5 days after treatment you can safely assume your infection had been cured.
3) You don't need to be retreated.
I hope this has helped. Best wishes-- HHH, MD