Got a few thoughts to add. Sorry if my observations feel like 2X4's. I'm just a stranger on the internet, outside looking in. I hope the following doesn’t offend – not my intention. The goal is to give you a few words of support from one betrayed spouse to another. Hope it will help.
Why is he so mean?
Faithfinder, manipulative people typically use the same three channels to manipulate those they hope to manage:
Rage/Anger, Self Pity, and Charm (being nice.)
He may surf through these channels randomly to hit on the most efficient method to manage you in any given moment. It's maddening! Your comment "his behavior is so confusing" is a sign that you are probably being managed as he flips through the standard manipulation channels. If your separation situation/dynamic is typical, he's probably been heavily tuned to the self pity or charm channels to kept you softened up to:
-Keep you lined up as plan B place to land in case things go south with OW, or a convenient place to park material goods that won't fit into his new apartment life. Responsible people (like you) may consider maintaining a "friendship" with their cheater "for the sake of the children" so make themselves into convenient doormats because "staying friends" is the "decent" way to behave. Staying "friends" also lets him control the narrative "yeah, it's hard but we're still friends." If you remain friends what he did can't be that bad, right? He's NOT your friend. This guy ABANDONED you and your kids. You don't need to be friends with him to successfully parallel (not co) parent!
-Keep you feeling sorry for him so he can mange you into securing a favorable $$/childcare settlement during D, or so you will excuse the no-shows with kids supervision, and during holidays because he's "having such a hard time." Making excuses for him with friends and family also serves his image management. Decent people (like you) with a normal stockpile of empathy are easy to manage with the self pity channel. Hypothetical example: He shows up at Christmas all teary eyed. Only stays briefly because "it is so hard for him to be here." Splits to go spend Christmas with OW. You and the kids may even feel sorry for him. Poor guy. When his goal all along was to spend that time elsewhere.
Faithfinder, you had the good judgement to retain a lawyer and file for separation, which doesn't work for HIS best interests. So now he's flipped to the rage/anger channel. To see if he can get you to back down by pushing your guilt buttons maybe? You are a functional human being with intact emotional wiring, so pushing your emotional buttons to get a desired reaction from you may be standard operating procedure for him. Google terms like DARVO (Deny, Attack, Reverse Victim and Offender), false equivalencies, minimization, etc. etc. and read up. "30 Covert Emotional Manipulation Tactics" by Adelyn Birch is a quick, concise 61 page read that covers most of the ways manipulators take control in personal relationships. Learning the game so he can't play it with you is key for you to keep your sanity during the separation. You may find that some of the emotional manipulation tactics outlined were always in play during your marriage. I know I did. I just didn't have the tools to identify these behaviors or the motivation to name them pre D-day.
Gray rock with minimal contact (kids or finances only at YOUR convenience) doesn't mean you're being harsh, or rude - you're being neutral. Gray rock/minimal contact protects you from his button pushing. And helps you gain distance, healing and clarity regarding your new life without him in it. Maintaining contact only prolongs the pain. Have you told his family/your friends what's going on? Servicing his image management to protect his family is not your job. They deserve to know the truth. If his family needs to be in touch with him politely extricate yourself from this duty. He's not your responsibility anymore. He made his choices.
This is none of my beeswax, but I noticed you filed for separation, not divorce. Wondering what the logic is to separating rather than divorcing? Why not proceed directly and cleanly to divorce? He discarded your family. You're working with a lawyer so I hope this was their strategy? Faithfinder, I'm in your corner, rooting for you to continue on your path out of infidelity. So glad you retained a lawyer and are taking some painful steps towards building a new life for you and your family.
ETA:
"Leave a Cheater, Gain a Life" by Tracy Schorn is another good read to help you decipher what's going down right now, and help to keep sane as you navigate your way.
[This message edited by BoundaryBuilder at 12:42 AM, Monday, January 24th]