Is it permissible for a woman to seek divorce from her husband who does not pray, does not fast, disbelieves in the Creator, and insults her parents, knowing that she has left the marital home several times because of this?

If what you mentioned about your husband's disbelief in Allah is true, then it is not permissible for you to return to him, for he is not lawful for you. Allah the Almighty has permitted the marriage of believing women to believing men and has forbidden them from marrying disbelievers, as He Almighty says: "And do not marry polytheistic women until they believe. And a believing slave woman is better than a polytheist, even though she might please you. And do not marry [your daughters] to polytheistic men until they believe. And a believing slave is better than a polytheist, even though he might please you. Those invite to the Fire, but Allah invites to Paradise and forgiveness, by His permission. And He makes clear His verses to the people that perhaps they may remember." (Al-Baqarah: 221).

Therefore, it is obligatory for you to annul the marriage immediately and separate from this man. However, confirming the validity of what you attributed to your husband and declaring him a disbeliever can only be done by a judge. Hence, you must refer to the Sharia judge so that he can ascertain the man's true nature and verify what you attributed to him.