We are truly sorry to hear about the struggles you're facing in your marriage. Let's bring your situation before the Lord in prayer and seek His will according to His word.
Firstly, we acknowledge that marriage is a sacred bond ordained by God, as it is written, "For this reason a man will leave his father and his mother, and will be joined to his wife. And they will be one flesh" (Genesis 2:24 WEB). It is not God's will for a couple to easily break this union apart. God hates divorce, as the Word says in Malachi 2:16, "He who hates and divorces his wife, says Yahweh, the God of Israel, 'covers his garment with violence!' says Yahweh of Armies. Therefore pay attention to your spirit, that you do not deal treacherously."
We must also address the underlying issues in your husband's behavior. The anger and threats are not reflective of the fruit of the Spirit, which is love, joy, peace, patience, kindness, goodness, faith, gentleness, and self-control (Galatians 5:22-23 WEB). Instead, they may be a sign of the enemy trying to gain a foothold in the relationship and destroy what God has joined together. We must also be clear that the scripture says:
Husbands, love your wives, and don't be bitter against them. (Colossians 3:19 WEB)
Finally, brothers, whatever things are true, whatever things are honorable, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report; if there is any virtue, and if there is any praise, think about these things. (Philippians 4:8 WEB)
We will pray for your husband's anger to subside and for him to seek God's will and peace. We will also pray for him to return home safely and for God to protect your marriage.
Let's pray together:
Dear Heavenly Father, we come before You in the name of Jesus Christ, lifting up our sister in need. Lord, You know the struggles she's facing in her marriage, the anger, and the threats. We pray for Your intervention, God. We pray for Your peace to reign in their home and for Your love to bind them together.
Father, we pray for our sister's husband. We pray that You would soften his heart and remove the anger and bitterness he's harboring. We pray that he would be drawn close to You and that Your Holy Spirit would convict him and guide him in Your truth. We pray that he would seek counseling with his wife and that their marriage would be strengthened and restored.
Lord, we also pray for our sister. We pray that You would give her the strength and courage to stand firm in her faith. We pray that she would draw close to You and that You would be her refuge and her strength. We pray that she would be a light in her home and that her husband would see Your love reflected in her.
Father, we pray for their marriage. We pray that You would protect it and that it would be a testament to Your unfailing love and faithfulness. We pray that it would bring glory and honor to Your name.
Lord, we also ask that he knows that leaving is not an option and that the threats are empty and meaningless in Jesus' name. We bind the devil and cast him out of their lives and marriage in Jesus' name.
In Jesus' name, we pray. Amen.
Remember, even in the toughest times, God is with you and will never forsake you. Stand firm in your faith and trust in Him. You did not specify praying in Jesus' name, but it is very important to pray in Jesus' name.
For through him we both have our access in one Spirit to the Father. (Ephesians 2:18 WEB)
There is salvation in no one else, for there is no other name under heaven given to people by which we must be saved (Acts 4:12 WEB)
If there is no other name by which we can be saved, then there is no other name that we should pray in.
Behold, I stand at the door and knock. If anyone hears my voice and opens the door, then I will come in to him, and will dine with him, and he with me. (Revelation 3:20 WEB)
that if you will confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved. (Romans 10:9 WEB)
Because if you confess with your mouth that Jesus is Lord, and believe in your heart that God raised him from the dead, you will be saved. (Romans 10:10 WEB)
We encourage both of you to confess with your mouths that Jesus is Lord, and believe in your hearts that God raised him from the dead, and you will be saved. Draw close to God, and He will draw close to you. We will continue to pray for you and your husband, trusting that God will work all things together for good.
Also, you referenced his being a former marijuana addict and that he has been sober for a number of years. It is important to realize that the word of God says: Be sober and self-controlled. Be watchful. Your adversary the devil, walks around like a roaring lion, seeking whom he may devour. (1 Peter 5:8 WEB)
The fact that he has been sober does not mean he is no longer tempted to fall back into his addiction. This is a warning sign that he may be under spiritual attack. This is especially important for you both to realize.
Prayer Focus: God, Thank You for loving me. Thank You for loving me, Jesus. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, soul, mind, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
