We understand that you're going through a challenging situation and commend you for seeking God's will in this matter. It's crucial to remember that God's ways are higher than our ways, and His thoughts higher than our thoughts. (Isaiah 55:8-9, WEB)
Firstly, we thank God that this man has turned to believe in Jesus Christ. Remember, there is therefore now no condemnation to those who are in Christ Jesus (Romans 8:1, WEB). His past sins, no matter how grievous, are forgiven and forgotten by God. As it is written in Hebrews 8:12, "For I will be merciful to their unrighteousness. I will remember their sins and their iniquities no more."
However, it's also important to address the anxiety and imagery that you're experiencing. The Bible tells us to take every thought captive to obey Christ (2 Corinthians 10:5, WEB). Whenever these images come to mind, rebuke them in Jesus' name and replace them with thoughts of what is true, noble, right, pure, lovely, admirable, excellent, or praiseworthy (Philippians 4:8, WEB).
Regarding your fear of Satan using his past to ruin your marriage, remember that God has not given us a spirit of fear, but of power, love, and self-control (2 Timothy 1:7, WEB). If this man is indeed God's will for your life, trust that God will equip you both to overcome any challenges that may arise.
Now, let us pray together:
Dear Heavenly Father, we come before You in Jesus' name, lifting up our sister who is seeking Your will for her life. Lord, grant her discernment and peace regarding this marriage proposal. Help her to forgive this man's past, just as You have forgiven us all. If this man is Your will for her life, Lord, give her a supernatural peace and help her to move forward with him. But if he is not, reveal this to her clearly, Father.
In Jesus' name, we rebuke any spirit of fear or anxiety, and we ask that You fill her mind with thoughts that are pure, lovely, and of good report. Equip her with the power, love, and self-control that come from You.
We ask all these things in the precious name of our Lord and Savior, Jesus Christ. Amen.
Lastly, we encourage you to continue seeking God's will in this matter. Trust that He will guide you and give you the wisdom and discernment you need. Be patient and commit your ways to Him, and He will act (Psalm 37:5, WEB). Always remember that "marriage is honorable in all, and the bed undefiled: but whoremongers and adulterers God will judge" (Hebrews 13:4, WEB). Stay strong, and feel free to reach out to us anytime.