I would peg that as your O day. I have a lot if charts that dip around 3 or 4 dpo. Not that drastically, but I have seen others that do.
As for the humidifier, also no idea. Consistency is good so if you can suffer through this cycle without it. But =/ not sure
Their family is falling apart because the foundation of it was never solid. Well, his mom.and I talked behind his back. She told me never to tell him. I wanted to because we don't keep secrets in my family, but she said it would also affect her relationship with him. Guess who decided to open her mouth and throw me under a bridge?