What alarms me most is that he’s not giving any cues to your face. You say the screen door incident left him incensed according to what he wrote to her, but if you’d never have read that you’d never have guessed.
I’m reading a lot about a woman who gives him a lot of care, attention and leg room. I’m also getting the impression he’s caring too and pulls his weight in other ways. But the narrative he’s feeding the other woman feels like there’s a deep resentment and a deep fear of confrontation at play. Or that he’s wrestling his conscience so much so that he’s spinning a yarn to convince himself that you’re truly a bad human and ergo, he’s doing the right thing by having this emotional affair.
Either way it’s not fair on you, because although you’re comfortable with an open relationship, these actions in fact close you off. They give you no chance to defend yourself, voice your side of the story or confront the issues claimed. It’s not fair territory, he definitely needs to come clean with these feelings to your face. But like others are saying, you need to protect yourself to ensure you don’t lose out any further than you already are by doing so. I'm so sorry you're going through this, please keep us posted - clearly many on here, rightly so, have your back, myself included! x