Your gut is telling you this is not right. Ignore it at your own peril. Talking to a man for several hours a day is totally unacceptable. Why would you allow it.
How do you know he's really distant. Could have a cell that is from another city but he could be local. Even if he is distant, they could have already gotten together. If not, they sure will try to get together at the soonest possible opportunity.
You would be blown away by the number of threads that start just like yours but turn out to be an affair. At the moment, it sounds like the beginnings of an EA. You have every right to fight for your marriage but insisting on boundaries. Talking to the opposite sex for hours a day should be considered outside of those boundaries.
You will have to go James Bond. I recommend that you get access to all her devices, social media, and email. Since you confronted her, she will likely have her guard up. Look for a burner phone. A VAR (voice activated recorder) velcroed under the passenger seat of her car can get you evidence very quickly. If she's not talking to OM, she may be confiding in some friend about having the hots for OM.
You better get moving. Strong actions get results. being understanding, opened minded, and not wanting to appear to be controlling will get you played.