Divorce due to Catholicism

A guy chiming in here...

He’s open to Orthodox Christianity, but he wants to research the religions to make a decision that is right for the family.
That is a good start.

He doesn’t like papal infallibility or original sin.
I would ask him: "What do you know about papal infallibility and original sin?"

Because from what you're saying about him, I'm willing to bet good money that what he thinks those two things are aren't actually what they actually are.

Don't have him look them up wikipedia on his phone, sit him down, and have him tell you what he thinks those two things are. THEN look up those things and ask him what he thinks about them. (I'd ask him after that, "You know that Papal Infallibility has only been used officially twice in history, right? The Immaculate Conception, and The Assumption. There are other instances from history that theologians say were Infallible, but they disagree on how official they actually are...")

Original Sin is what proves Christianity correct, but that's just me...

Christianity can be summed up as "Sh*t happens, just look at any Crucifix. If that's what happens to the best of us, guess what you're in for..."

Hate to say it and to use you as an example, but this is why a marriage based on Christ is superior to one that isn't.

Our relationship is wonderful! I was a non-practicing catholic from the beginning of us, 20 plus years ago.

His mom is bpd-narcissist who uses her Catholicism to shield her from any sin or blame / she likes to say she’s 99.9% pure.

He thinks it’s mind control and said no to mass even if it’s just me and not the kids, but I think lying low and being patient is where I need to be.

(Usually it's the classic "daddy-issues" that people have with this sort of thing, ESPECIALLY with the idea of God being a Father. It's very common to come across things like: "My father was a horrible person, so God the Father must also be a horrible person too!" for example.)

I would press him for why he thinks it's "mind control." I'd gently push for specifics. I'd argue that if the Church is doing "mind control", the fact that the Church has the Sacrament of Confession, it's doing a very bad job of it. If the Church could control people's minds, Confession wouldn't be needed at all. (One could argue, that the modern world has done a better job of "mind control" in the last 70 years than the Church has done in the last 2000 years.)

Your husband has issues with his mother, we've all got our own baggage. (I've got A LOT of baggage with my own family for what it's worth.)

Whatever that "baggage" is, that isn't an excuse to walk away from your Eternal Salvation.

Especially with your children. Those are souls entrusted to you by Almighty God.

I'm pretty gosh-darn "traditional" and under a lot of conditions, I would tell you: "You should submit to your husband in this case, it's not a big deal."

Not this case this though.

Unless he has something CONCRETE, like: "Here's a news article/a report I found, the priest (or deacon, or youth leader etc.) at this parish is a danger to our children, you cannot attend services there." You should make a stand, "This is only one hour or so per week on Sunday. This is important to me. You do not have to attend. You can continue to research on your own, and come to me with ideas you have, but until then, I'm doing this." This either is the most important thing in your life or it isn't, and would expect nothing less from my own wife to be honest.