Apologies OP, that should have read "lovely".
Unfortunately when things get to a stage that a 4 year old is running the home, you are really going to have to decide yourself how determined are you to turn this around.
The reason your son is a persistent, demanding child is that he has been taught that this behaviour works.
You can't blame him for behaving in a way that he knows gets him EXACTLY what he wants.
He knows that NO means nothing.
Nagging by my children NEVER worked because a) it pissed me off hugely, and b)it made me even more determined to let them know it wouldn't work.
Children stop doing what doesn't work.
They are very clever that way.
You need to stop giving into him.
Let him scream and shout until he is worn out, however long it goes on.
Walk away from him.
Ignore him.
Don't give oxygen to his misbehaviour.
Take any technology away from him.
Remove his favourite toys.
Keep removing things he likes and don't give them back until he gets that you mean business.
Do not allow him to interrupt your conversation and contine.
Stop him with a 🤚and ask him calmly "please do not interrupt, mummy is speaking", and mean it.
Consistency is the most important thing.
Children are driven by self interest. They will only change their behaviour through self interest.
Asking them to not do this or that rarely works.
They usually change their behaviour because they realise it is to their advantage.
This is why you have to be firm, resolute, calm, consistent.
You need to make it very very clear that his tantrums, rudeness, bratty behaviour will no longer work.
Obviously you need your husband to be onside for best results.
Good luck 