Bismihi Ta'ala

Wa alaikum salam

It is very encouraging to see that you are supporting a family on your own.
May Allah give you steadfastness, strength and patience.

On the other hand, it is equally important that you re-marry as this is the need of every human being, no matter how strong. Eventually you will feel lonely. The best way to protect ones Imaan is to marry as this guards ones chastity, morality and many other things.

Regarding re-marrying your ex-husband. You did not mention the manner of the divorce. Was it three divorces or one or two? The Shar'ee (legal) rule will vary according to the manner of the divorce.

If he divorced you three times, you cannot return to him until a Shar'ee Halalah has taken place. If there was only one or two divorces then you may return to your husband.

My advice is that you must be very careful before taking this step.
Cautiousness is a sign of a believer. Rasoolullah Sallallahu alaihi wasallam
said: A believer is not trapped into the same hole twice. This means that if you feel you made a big mistake once, you may want to give this a long hard thought. Consult your loved ones. Look out for the best interests and concerns of yourself and children. Try to do some research about him again.

Find out if he has given up his old habits. Old habits die hard and to give up a habit like gambling is very difficult. Once given up it could return in an instance as the attraction is very strong.

Also, if it is Halal for you to return to re-marry him according to Shari'ah, then before doing so, you should do Istikharah, as this is asking Allah to put Khair (good) and Barakah (blessings) in your decision.

May Allah Ta'ala guide your heart towards that which is best for you, your children and you Imaan.

And Allah knows best.