Please provide where I can look up the torah/talmudic law governing this sensitive subject matter: Can a man divorce his wife, marry a 2nd woman, have a child with the 2nd woman, then divorce her and remarry the first woman?

See Devarim [Deut.] Chapter 24 verses 1-4. It couldn't be clearer.

What if the first wife didn't remarry?

What you have referred me to reads:
24:1 When a man marries a woman or possesses her, if she is displeasing to him [or] if he has evidence of sexual misconduct on her part, he shall write her a bill of divorce and place it in her hand, thus releasing her from his household.
24:2 When she thus leaves his household, she may go and marry another man.
24:3 However, if her second husband hates her, and therefore writes her a bill of divorce, placing it in her hand and releasing her from his household, or if her second husband dies,
24:4 then her first husband who divorced her cannot remarry her, since she is now forbidden to him. To do so would be repulsive to God, and you must not bring immorality to the land that God your Lord is giving you as a heritage.

It doesnt mention as,raybin asked, what if the original wife did not remarry and was waiting for her ex-husband to remarry her because he said he would?

quote:

It doesnt mention as,raybin asked, what if the original wife did not remarry and was waiting for her ex-husband to remarry her because he said he would?

That wouldn't be a problem unless the husband was a Kohen. A Kohen is forbidden to marry a divorcee, even his own ex-wife.

I think I misread Sarah's original question (or perhaps it has been edited).

My response was to cover the situation where the wife had remarried (and then divorced) in the interim.

If, however, the wife did not remarry, but her husband did do so, then there's again no problem from a Torah point of view as a man is permitted by the Torah to have more than one wife. And it wouldn't make any difference if the husband were still married to the second wife or of he had divorced her.