Wa alaikum salaam wa rahmatulahi wa barakatuh sister,
It is sad to read that after a strong marriage for so long that things seem to be falling apart now. It is understandable why this is causing you such distress.
Let me begin by reassuring you that you are doing a good thing to remain strong for the sake of children. Stepping back and leaving it to Allah will make things a lot more comfortable for you. So, even though times are difficult never give up on this and continue to pray to Allah to change things for the better.
However, sitting back and doing nothing about it will not change things, you also need to be active in encouraging this change also, so amongst the du’a there are some other things you can try too to ease the situation.
Make sure to continue to take of yourself, eat well, exercise, sleep well and mix with others. Give yourself something positive to rely on in your life also that will continue to give you boosts in your wellbeing. You could also make this a part of being a positive influence on him.
So, for example, if you have friends who you know have good husbands who you would be happy for your husband to spend time with, then you might consider asking them around for dinner. This way you can feel comfortable that your husband will be mixing with a good man who might in sha Allah have a positive influence on him and might overcome his desire for friendship with the people who seem to be having a bad impact on him.
If it is a case of black magic then make sure to protect yourself and your household from this. We should always take care to do this anyway as the likes of an evil eye..etc. can be cast any time even by people without knowing. Make sure to say your morning and evening adhkar and a means of protection all day every day and doing other acts such as reciting or playing Surah Baqarah in your house is also a good way to protect you from such calamities also.
Make your du’as at the best times, so when in sujood, or whilst praying tahajud or when breaking your fast if you ever offer any voluntary fasts. Then are many authentic du’as to be read during times of distress, but remember it’s not necessarily that reading more of them will make them any more effective, but it’s about the sincerity when you offer them and having the conviction that Allah is listening and will answer you and make things easier.
As for the messages being sent to both you and your husband try as much as possible to disregard them and encourage your husband to also as paying attention to them and allowing them to affect you will only impact on your relationship more which is possibly what this woman wants, or if not her, then certainly the Shaytan loves to sow discord between husband and wife.
It’s quite normal for marriages to change with time, especially after having kids and it can be quite easy to attribute these changes to other things, such as the influence of others, so also try to see it as something that might just have occurred due to becoming used to each other. So, in addition to protecting yourself from what might have happened, do also work on your relationship as a couple to try and put that spark back where it seems to be missing.
Do fun things together that you both enjoy, spend time alone together, ask someone you trust to take care of the children for a few hours so that you can be alone together and either go out for dinner or cook for him at home, just the 2 of you. Talk and laugh about times you’ve had together and try to reignite the spark that was once there. You might even try something new together, start up a new hobby together, something that you can work together on and support each other.
Be patient, never give up hope, if you are doing everything required and asking Allah then surely, He will help you at the right time. But for now, see it as attest, do all you can to protect yourself and your family and continue to a be a positive influence on your husband and in sha Allah he will snap out of it.
May Allah help you to overcome the difficulties you face in your marriage at present and make it easy for you to remain strong, patient and steadfast. May He bring you happiness and contentment into your marriage in both this life and the next.