I might just go for legal separation since it'll probably cause a lot less friction between my husband and I, right?

You do understand that this means you're still tied to your husband forever? In the event of any kind of abuse, this option can't stop him from pursuing you and your children.

You can also make a case for your own psychological incapacity. But that might affect your chances at securing custody of your children.

Then, should I just go for nullity? Hmm, the best way to go would be to try and prove his psychological incapacity. But what if I don't have enough evidence?

I don’t know where to go from here. None of these are ideal.

Only you can decide what's best for you and your family.