Jesus death paid the price for our sins, which now makes it possible for us to have our sins forgiven. If he would not have redeemed us, we would not be able to have our sins forgiven. As such, we would have no hope of attaining heaven, no matter how many times we repented and no matter how holy our lives became. We would be without hope.
Jesus’ sacrificial death and infinite merits do not cover our sins; rather, his sacrifice satisfied the justice of God and made it possible for us to have our sins washed away. Not covered over, but washed away.
No. He sends His grace but we have to receive it willingly and cooperate.
Regarding Jesus’ death for our sins. Through His death He merited the restoration of “life” to our souls (sanctifying grace). When Adam sinned death entered; not just death of the body, but death of the soul. Nothing, absolutely nothing, we do could ever restore that. We’re just simply incapable of it. Jesus merited a restoration of life - life in the soul at Baptism; life in the body at the final resurrection. Mortal sin destroys that supernatural life in our soul; separates us from it. Without it we cannot enter heaven. We do not merit the grace, it is freely given in Baptism; but we can lose it through our sinful deeds.