What is it about the decretum absolutum (absolute decree i.e., predestination in determinist mode) that sinks the classical Calvinist understanding of a doctrine of God in a God-world relation? It’s that it operates from an instrumentalist understanding of the Son’s relationship to the Father; it ruptures the eternal bond between the Father to the Son by the 
Spirit as the Son incarnates and becomes human. Under such conditions the work of Jesus is no longer essential to the being of the Son (and thus the Father), as such He simply becomes so much a demi-urge carrying out the dictates of an ad hoc decree (also not essential to God’s eternally triune being); meeting the conditions of the covenant of works/grace (having been ordered by the pactum salutis); and thus, an organ of God, but not God in se.
When the classical Calvinist system is placed under Christological scrutiny, through the analogy of the incarnation, it fails, radically so. Its centraldogma of predestination, in a God-world relation, as noted, reduces to, at best, a Ebionite christology, wherein the Logos ensarkos (‘Word enfleshed’) is ripped from the womb of the Father, thrown asunder among the heathen humanity, becoming the denarii by which the Father purchases the ‘elect’ from the ravages of the fallen world. When the works of Jesus are separated from the person of Jesus (think the Patristic an/ -enhypostasis), and this is what happens under the decretal system of Federal theology, or Westminsterian Calvinism, the Son in Christ simply becomes an elevated human, an adopted appendage who has been given the status of purchasing power in the stock market of the Father’s economy.
People living under the weight of the classical Calvinist schemata need to really think, and research deeply in regard to these above charges. Attempt to see if what I am asserting (and somewhat arguing) be so. Think through the logic and implications of the incarnation; think from the ground and grammar of the triune life of God. If after scrutinizing thusly, and you still believe classical Calvinist theo-logic holds up under the pressure of a strict adherence to God’s Self-revelation/exegesis in Jesus Christ, I will pray for you. Let me know if you need prayer.