I think we are all trying to understand how the Holy Spirit works, and in relation to the Sacraments. An important reality, is that we cannot know the depths of the Lord in this way.
I agree with all Christians who believe the Spirit is working for the conversion of all men and women from the earliest moments of coming into the age of reason.
I also believe He desires our children to be made holy through our privilege as parents who are able to bring our children to the Lord for this grace. “Otherwise, they would not be clean”
The Lord stands at the door and knocks. The Father beckons us to the Son! And His spirit goes where it will. “We know not whether it comes or goes”.
But we are not ignorant of His promises either!
The Spirit is called on at Baptism! The earliest conversions were not always aware of the accurate understanding of the faith. Yet there was genuine faith to convert, enter into Salvation, and grow in knowledge and charity.
How do you explain the Laying on of Hands? The early Church fathers attest to this practice as a significant practice in the life of a Christian. It was a means of conferring a blessing and grace to a Christian by strengthening their call!
You seem to acknowledge that an adult can faulter in his knowledge and sincerity while receiving Baptism, but God still bestows a certain grace nevertheless.
How do you understand Hebrews 10
Do you not think that a much worse punishment is due the one who has contempt for the Son of God, considers unclean the covenant-blood by which he was consecrated, and insults the Spirit of grace?
Is it possible that this grace has come through the Sacraments of Baptism, Comfirmation (Laying on Hands), and Communion?