RE: “The inheritance of sons is given us through Holy Baptism, in which God the Holy Spirit makes us all sons of God by faith.”

Saving faith may also be obtained before baptism, as "the wind blows where it wishes." (John 3:8) And here are some Bible verses that speak of being a son or child of God in terms of actual behavior:

“Love your enemies and pray for those who persecute you, so that you may be sons of your Father who is in heaven.” (Matt 5:44,45 ESV)
“For whoever does the will of my Father in heaven is my brother and sister and mother.” (Matt. 12:50 ESV)
“Do all things without grumbling or disputing, that you may be blameless and innocent, children of God without blemish.” (Phil 2:14, 15 ESV)
“Therefore be imitators of God, as beloved children.” (Eph. 5:21 ESV)
“For all who are led by the Spirit of God are sons of God.” (Romans 8:14 ESV)
“Blessed are the peacemakers, for they shall be called Sons of God.” (Matthew 5:9 ESV)

Our adoption signifies not only our eventual inheritance but also our blessed calling this side of heaven. Sonship is an identity which is already our privilege and joy to fulfill as God gives the grace.