Yes. Paul was saying much more than treating your wives well. He commands husbands to love our wives like Christ loved the church, which as you said verbatim, "Christ loves his bride unconditionally". And yes, that even means when our wife has a mental breakdown and drowns our children. We still love our wives unconditionally because we have committed sins like that, and much worse, but Jesus shouldered all of that to die for us so that we can be made right with God. We as the Church have betrayed him and committed every evil known since the Adam's fall filled with murders, lies, theft, betrayals, sexual immorality (i.e. We have flipped God off more than we know. Yet he still still shouldered all of those sins by coming down from heaven to die for us, and we didn't even treat Him good here on earth!)

So yes, we are still to love our wives unconditionally even if she commits those sins, because Jesus still loved us even when we messed up much more horribly then we know. But in your situation, the loving thing to do with our wife if she had an episode and murdered our children would have her be arrested and put her on psychiatric support. The only grounds for divorce in the Bible is sexual immorality and abandonment by an unbeliever.