1. The early church taught a substitutionary, propitiatory, sacrificial death as the key to Christ's 'sweet exchange' with sinners.
e.g. For Irenaeus, Christ's filling out of Adam's distorted image necessitates a 'filling up of the times of his disobedience' (Ad. Her. III.21.1). In taking on Adam’s substance, He took on Adam’s curse, satisfying it at the cross, ‘propitiating indeed for us the Father, against Whom we had sinned’ (V.17.1) and ‘redeeming us by His own blood' (V.14.3).
For Athanasius the curse of Genesis 2:17 is key. The Word becomes incarnate in order to take a body capable of death “so that in His death all might die, and the law of death thereby be abolished." (De Incarn. 8) Moreover this death is specifically a sacrifice (ch9; 10; 20) made under God’s curse (ch25).
2. Penal Substitutionary Atonement (PSA) cannot mean a disruption to the Father-Son love since God's wrath is an aspect of His love. Perhaps if we thought that wrath was some other thing, divorced from love, then we might say that God's wrath poured out at the cross breaks the Father-Son union. But no, if God is love and if this wrath is a reaction of love to the sin that Christ had become, then there is no danger of breaking the homoousios.
3. PSA means God saves us from God. It says that the ultimate problem facing humanity is not death or corruption or sin or the devil but God Himself. Sin is not our real problem - wrath is. We need to be saved from the Judge Himself. And we can only be saved by the Judge Himself - the Judge judged no less. Certainly Christ ransoms us from all those lesser powers (and therefore certainly there is a place for Christus Victor etc). But that's not the ultimate meaning of salvation. It's a divine curse, a divine judgement, divine wrath from which we must be delivered. PSA takes this with the seriousness it deserves.