I think this was all face-saving stuff KB said to comply with her faith community and to made her unmarried pregnancy less of a black mark on the name of her family.
I don't believe HE gave her any ring or any sincere discussion of a wedding. If she had a ring, I believe she would have bought it herself. I also think the August visit to the SDA center for depression probably was because she realized he was not ever going to marry her and legitimize her child.
I think that's when she realized what a bad position she was in. She was buying a condo, so that complicated making a move. I'd be surprised if she knew that under Colorado law, as I understand it, she couldn't move out-of-state with Baby K without PF's OK. The work commute was wearing her down and obviously if there had been good job prospects closer to home, she would have gone for them. She's geographically isolated from her family and friends, it doesn't appear that PF's family and friends ever embraced her, and her work friends were hours away.
And yes, I think that's also when she realized he probably wasn't ever going to marry her. I think in early 2017 she told someone at work she wasn't sure when they were getting married, but she hoped soon. I remember thinking that at the time of the conversation, she must have been in the earlier months of her pregnancy. It seems to me that whoever she was talking to might have known she was pregnant, but I could be wrong about that.