Q n A : Her son controls her

Praise be to Allah.
The way your husband’s mother has behaved is strange. How can
her son control her and make her act in this manner? But despite all that
your husband has to honour his mother as much as he can, and Allaah does not
burden any soul beyond its scope. If he can visit her when this son is not
present, that is good. If he can keep in touch with her by phone, then let
him do so, and explain to her what he feels, this is good as well. If he can
get some people to intervene, women and others, who can influence his
mother, then let him do so. And he should seek the help of Allaah and make a
lot of du’aa’. 

The fact that your husband defended himself in court and in
front of the police is also good. 

If he takes his brother who wronged him to court to stop him
from doing more harm, that is permissible, but if he bears it with patience
that is better for him. 

Trying to get your husband’s mother away from this oppressive
brother (as described in the question) is a good idea, so as to remove the
means that your brother is using to try to control the whole family. 

There is nothing wrong with you stopping visiting her for
now, until things settle down, so that you will not be harmed again as
happened before, especially since your husband’s mother is not one of your
relatives with whom you are enjoined to uphold ties and honour them. If you
do not visit her this is not regarded as disobedience or severing of family
ties. 
Yes, you will be
rewarded for visiting her and treating her kindly, if you do that sincerely
for the sake of Allaah, and this is part of treating your husband kindly,
but it is not obligatory for you to do that, especially since she is badly
behaved and has a bad attitude. And Allaah knows best.