After persons are justified by becoming Christians in baptism and entering the state of grace, can we be justified to a greater extent, or have an increase of faith, hope, and charity, by faith and good words, OR is justification just a simple case of on or off, justified or not, with no possible increase?
Yes! And there’s no end to the amount of justice we can grow in because the model is God, Himself, whose image we’re to be transformed into. Here’s the Council of Trent speaking on it, session 6:
CHAPTER X
THE INCREASE OF THE JUSTIFICATION RECEIVED
Having, therefore, been thus justified and made the friends and domestics of God,[49] advancing from virtue to virtue,[50] they are renewed, as the Apostle says, day by day,[51] that is, mortifying the members[52] of their flesh, and presenting them as instruments of justice unto sanctification,[53] they, through the observance of the commandments of God and of the Church, faith cooperating with good works, increase in that justice received through the grace of Christ and are further justified, as it is written:
He that is just, let him be justified still;[54] and, Be not afraid to be justified even to death;[55] and again, Do you see that by works a man is justified, and not by faith only?[56]
This increase of justice holy Church asks for when she prays:
“Give unto us, O Lord, an increase of faith, hope and charity.”[57]