In What Way Can Catholicism Speak of a Substitution of Christ and Us

I have a (formerly Lutheran, now Driscollite / neo-neo-calvinist) friend who said to me one night with much frustration across a kitchen table: "what do you believe the Cross even did?". I think I honestly and jokingly answered 'nothing' but I might've used a quasi-arminian "potentiality" explanation.

The problem seems to be, with all of our anti-Protestant theology we Catholics rapidly lost the ability to speak of God's efficacious grace and the salvation won on the cross as a solid theology. Rather now it seems to be a theology based on human will and potential salvation rather than divine will and efficient salvation.

As far as I can see, Catholicism objects to the notion that the Father punishes the Son for atonement of the sins of the elect, and that they instead stick with St. Anselm who phrased it more along the lines of: Christ did something good for God which we couldn't do, but which we were obligated to do. Thus somehow through baptism, penance, etc, we get that goodness (Merit?) applied to us.

Correct me if I'm wrong there.

I really want to get as close to Penal Substitution as possible within Catholic orthodoxy, because it makes me feel at ease and allows me to rest from trying to frantically accumulate merit.

It's so hard to distinguish between St. Anselm and Calvin for me. There is such a fine line when discussing what Christ did in a substitutionary manner, and what he didn't do. Like I think it's Morally, and Meritoriously proper to say Christ acted on our behalf, but not legally.... Aquinas' scholasticism confuses me at times, at least Augustine's neo-platonism was easy to get.

Then you have Hans Urs Von Balthasar who basically made Penal Substitution Catholic by saying that a finite amount of sin was placed between the infinite distance of the Father and the Son and burned up completely by their love. This is my favourite of all atonement models, and while it was taught by a fairly orthodox and highly respected Catholic theologian, many traditionalists probably dislike it because they'd say it tends towards universalism and is too similar to Penal Substitution, even though it technicaly avoids the anathemas.

If it's possible to hold Von Balthasar's Christology/Soteriology while remaining within Roman orthodoxy, then I'd like to hold it, I just don't know enough.