How can God be loving and just whilest creating people for His wrath? I cannot wrap my head around Calvinism!

I just recently left a church that I attended for nearly a decade that is rooted in Calvinist beliefs. I am really struggling with their conception of the Lord and their understanding of the scripture. I have had many belabored discussions with friends that remain in the congregation and despite their zeal I am unconvinced. **Please help me understand how God can be characterized as merciful, just, and righteous within the Calvinist framework.** The argument that we all deserve God's wrath will not suffice because — while I certainly agree that all have sinned and fallen short of the glory of God, and that the wages of sin is death — if predestination is true and we don't all have the opportunity to choose Jesus, then God cannot be just. We were born into a sin nature. We cannot choose to not be born and we cannot choose to not sin. We are incapable of being sinless. That being the case, if we are born into sin AND we also do not have choice in whether to repent and accept salvation through Jesus, then we must admit that God himself is really sending some people to hell. Such people cannot be said to be guilty. And God cannot be said to be just. If sin warrants death, and one cannot choose to reject one's sinful nature, and one also cannot choose the covering of that sin (Jesus), how can one justly be damned to hell? ---- I know this is a simplistic and silly framework but humor me: if I were to adopt a puppy, refuse to take him out, and then beat him for messing in the house, how would that be just? A puppy has no choice but to relieve himself. He was created with a bladder without consent (sin nature). Now if he is allowed to go outside to relieve himself, but chooses not to take advantage of that opportunity and then pees in the house, though he had another choice (free will for lack of a better term), then there is certainly some culpability (damnation). And before you respond with: we have no right to question God. He is the potter; we are the clay. Fine. He certainly does have such authority but that doesn't make it just. And it certainly doesn't make it loving. This proves axiomatic even to our fallen hearts and minds. We, being evil as we are, recoil at such cruelty. We do not condone parents abusing their children. Quote all the scripture you want. Throw out Romans 9. I am not here to debate scripture. Assume your understanding of scripture is accurate. Just convince me that it is just. And no, this is not a rant, this is a sincere question that countless hours of discussion have not satisfied. I have been reading ferociously for weeks trying to reconcile this in my heart and mind. I found myself going back and forth because there are compelling arguments for both. I wept for nearly 24 hours over this because I have never in my walk felt so confused. I have reached out to my pastor about this matter but he has been too busy to sit down with me yet and in the meantime I am distraught. A wonderful friend of mine from our local seminary spent five hours with me two weeks ago trying to answer all my questions, but he could not sufficiently address the justice part. The implications of Calvinism are difficult to accept and I want to arrive at truth. I am a devout follower and I am seeking understanding.