Silverhair

We can add these two that speak to the work of all three in salvation.
Mat_28:19
Tit_3:4-6

The Trinity and the work of the trinity in our salvation is laid out in this one verse. {1Pe_1:2} Those that wish to deny the Trinity would have to explain away the clear words found here.
God the Father
sanctification of the Spirit
the blood of Jesus Christ
The Trinity at the best of times is a challenge to explain.
I heard it explained this way: There are three who's; Father, Jesus, & Holy Spirit and one what GOD.
The Bible is clear when it speaks of: God the Father, God the Son, and God the Holy Spirit.
But states that there is only one God
"Hear, O Israel! The LORD is our God, the LORD is one!" Deu_6:4 cf Mar_12:29
If we were to use math, it would not be, 1+1+1=3 this would be polytheism.
It would be 1×1×1=1 this is monotheism. God is a Triune God.
Trinity is clearly shown in the bible. See Act_2:32-33, Act_7:55, 2Co_13:14, 1Pe_1:2.
The Trinity is clearly seen in the baptism of Christ Jesus Luk_3:22
So to answer your question; who is the one true God? God is a Trinity so whichever you speak of; Father, Son or Spirit you are speaking of the one true God.
I hope this helps clear up a hard to grasp concept.

Calvinists are not teaching heresy. What they are teaching is an errant view that is based on a misreading of scripture. All calvinists believe in the sufficiency of Christ in their salvation.
By using your logic "we are certainly saying X doctrine is false when compared with the Bible." All of us could at sometime be said to have taught heresy by some group that disagrees with our views. 
I have been called a heretic more then once by calvinist's because I disagree with their view.
I would say the JW's Mormons and Islam are all teaching heresy as they deny the work of Christ for salvation.
Again calvinism, as the people I have dealt with understand it, is errant but it does not reach the level of being heretical but taken to what I see as it's logical conclusion it would step over that line.
Following is a quote from Dr. Roger Olson April 19 / 2024. It is a good article that has good insights re calvinism.
"I will say it again, I consider Calvinists authentic Christians with defective theology that, if taken to its logical conclusion, makes God monstrous. Fortunately, most Calvinists do not take Calvinism to its logical conclusion and/or settle into some kind of inconsistency, claiming that God loves even those he predestines to spend eternity in hell for his glory." Roger E. Olson  https://www.patheos.com/blogs/rogereolson/2024/04/why-calvinism-cannot-be-true/
 

You're right - no one can will to be regenerated. But we certainly can respond positively to God's offer of salvation, then HE regenerates us (NOT BEFORE).
To be blunt, how do YOU know you ARE saved if you never responded to the Lord Jesus Christ nor received His gift of salvation, nor personally trusted in His finished work? Sounds like you might still be unsaved. The Bible teaches we can KNOW.
1 John 5:13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
Pity the poor person who has no assurance of personal faith or salvation in the Lord Jesus Christ because they never made a choice of their own. We don't find anywhere in the Bible that God forces people to be saved, nor regenerates them against their will.

The arguments given here against Calvinism are profound, and scripturally true. But I am a simple man and to me it all boils down to a very simple argument and verse.
If Calvinism is true, then God deliberately creates THIS person for Heaven and then He deliberately creates THAT person for hell. 1 John 4:8 tells us that God is love. I'm sure that person that the Calvinistic god deliberately created for hell sure sees the Calvinistic god as love.
I just cannot cross over that very simple hurdle. And no Calvinistic argument can change my mind. God is love. And He wants to share that love with whosever will. My loving God has NEVER created anyone for hell. If that is where you end up it was entirely your choice. 

FYI I am not a calvinist but I have dealt with calvinist's on other boards. Calvinism is not heresy. I would say that most have a great love for God but they error in their understanding of the means of salvation. Some are just a "bit" more zealous in their support of the TULIP / DoG.
Where they error is they start with the calvinist philosophy and then search scripture in the hope of finding a verse to support their view even if they have to twist the text or change the meaning of words.
It seems you encountered a more zealous one who trust what some man tells him the bible means rather than actually trusting what the bible actually says.

Calvinists teach that God’s elect have eternal life before they can come to Christ to receive eternal life.
Calvinists teach that we must be born again with life from the Holy Spirit before we may respond to God in any way.
“A cardinal point of Reformed theology is the maxim: ‘Regeneration precedes faith.’ [R.C. Sproul Chosen By God, pp.72-73].
“A man is not saved because he believes in Christ; he believes in Christ because he is saved”. [L. Boettner The Reformed Doctrine of Predestination, Page 75]

If Calvinism is true then faith in Jesus is secondary to election and logically faith plays no part in your salvation, election is what matters not faith.

The Calvinist asks: “How shall they believe if they have not been regenerated?” whereas Christianity asks: “How shall they believe if they have not heard?” Rom_10:14; Joh_5:39-40

Calvinists teach that God’s elect have eternal life before they can come to Christ to receive eternal life.
Calvinists teach that we must be born again with life from the Holy Spirit before we may respond to God in any way.
“A cardinal point of Reformed theology is the maxim: ‘Regeneration precedes faith.’ [R.C. Sproul Chosen By God, pp.72-73].
“A man is not saved because he believes in Christ; he believes in Christ because he is saved”. [L. Boettner The Reformed Doctrine of Predestination, Page 75]

If Calvinism is true then faith in Jesus is secondary to election and logically faith plays no part in your salvation, election is what matters not faith.

The Calvinist asks: “How shall they believe if they have not been regenerated?” whereas Christianity asks: “How shall they believe if they have not heard?” Rom_10:14; Joh_5:39-40