Support your old father. Speak to your brother when he is calm
Stand your ground where it is crucial and let go off the trivial issues
Love is never abusive. If your little sister was being beaten up what would you tell her?
Start by beginning to take care of your own happiness. Seek financial independence for yourself. Remember whatever you do, you are a role model to your daughter.
It is great to be in love yes, but tread carefully. The best of relationships can give in to financial and social differences. Think clearly and calmly about your future, discuss the details with your boyfriend and your family before taking any final decision.
You deserve happiness. Find a job to help your sense of self-worth. Meet a psychologist to help heal the pain.
Consult a therapist to identify possible causes, have an open conversation with your partner
A visit to a psychologist/psychiatrist would be beneficial
The children can file for maintenance
Directly file under Section 13 of the Hindu Marriage Act