Is it O.K. for spiritual talks to be held in the church and at the podium if the church has no other suitable location?
I would think as long as it is church related, it is okay. I have had Knights of Columbus ceremonies at churches, and I know on EWTN, Fr. Corapi has had some talks from the pulpit.
The parish I use to be at usually had thier lenten series held in the Church. However, the speaker (usually the Weekend Assistant Priest) always spoke off the Sanctuary area at a podium set up for the talks.
We also has some education series held in the day chapel with the same setup.