Praise be to Allah.
Our sister, may Allaah grant you relief from your distress, make things easier for you, and guide you to that which is good.
One of the decrees of Allaah is that He tests His slaves in this world to see if they are patient and content (with His decree).
“Great rewards come from great tests. When Allaah loves people, He tests them, and whoever accepts that earns Allaah’s pleasure, and whoever is angry with that earns Allaah's wrath.”
(Hadeeth narrated by al-Tirmidhi, 2396; classed as hasan by al-Albaani in al-Silsilah al-Saheehah, 146).
So be patient and seek reward.
With regard to what you mention about your husband, it is regrettable. He has committed three haraam actions:
1 – Not spending on you and your children. The husband is commanded to spend on his wife and children. If he fails to do that then the wife has the right to refer the matter to the court, and she may also ask for divorce.
2 – His neglecting to look after his household and children is a sin on him, even if he claims that this is for the sake of da’wah, because his soul has a right over him, and his wife has a right over him, and his Lord has a right over him. He must give each of them his right. The Prophet (peace and blessings of Allaah be upon him) regarded neglect of those who are under one’s care as a sin, and he (peace and blessings of Allaah be upon him) said: “It is sufficient sin for a man to neglect those whom he supports.” Narrated by Abu Dawood, 1692; classed as hasan by al-Albaani in Saheeh Abi Dawood, 1484.
Raising children and looking after them and the house is a trust that rests on the father’s shoulders. The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Each of you is a shepherd and each of you is responsible for his flock… the man is the shepherd of his household and is responsible for his flock.” Narrated by al-Bukhaari, 893; Muslim, 1829.
3 – Taking drugs is a haraam action, and indeed is a major sin. It corrupts a person’s religious commitment and his worldly interests, as well as damaging the body and mind, wasting money, and destroying honour. It includes all kinds of evil.
So beware of opening the door to it and falling in its trap.
How many households has it destroyed, how many people has it killed, how many blessings has it ruined, how much calamity has it brought about!
When people fall into the trap of drugs, hardly any are saved therefrom, except those upon whom Allaah bestows His mercy and guidance.
With regard to your desire for divorce, if your husband is sincere in his repentance and truly regrets what he has done, and is determined to reform himself, and if you still want him, then be patient and seek reward for staying with him. Perhaps Allaah will reform him, especially if he has asked you to stay with him and to wait for him. The fact that you have children together may also make you think more carefully before you ask for a divorce, because it is better for children to be raised with both their father and their mother than for them to be raised by one parent only.
If the man is sincere in his repentance and his regret (of the past), then it is better for you to be patient and to wait until he comes out of prison, because that is in his interests and in the interests of your children, and also in your own interests.
But if you cannot bear to be patient and to stay without a husband for this length of time (one year), or if the man is not sincere in his repentance, there is no sin on you in that case if you seek a divorce, and there is nothing good in your staying with him when he is persisting in that sin.
You have to make a great deal of du’aa’ to Allaah, and seek His guidance by praying istikhaarah before you take any step. For information on how to pray istikhaarah, please see questions no. 11981 and 2217.
May Allaah set your affairs straight and guide you both to the Straight Path.
And Allaah knows best.