OP, in life many many people waste years pursuing a relationship with people that are largely ambivalent about them.
A truly terrible waste, that when the penny eventual drops can often precipitate huge regret and grief.
Others will twitter on about relationship's not being transactional, not giving to receive and all that twaddle!
I firmly believe in reprocosity in relationship's.
Not 50/50 exactly to the letter, but more in principle.
That to have a mutually beneficial relationship with any one that I am interested and invested in, .....they too must have a similar interest in my general life/wellbeing etc.
Anything else is unsatisfactory, one-sided, and ultimately a waste of MY time.
This applies equally to family.
If they have zero interest in you, you don't have to cut them off, you simply reflect back a similar commitment level to them.
It is hugely energy preserving.
I am so sorry about your mum, that is very hard and painful.
If they have to be told to do something so absolutely basic as send a kind text, I really wouldn't waste precious energy on them.
They cannot give you what they haven't got.
Focus on your mum, yourself and accept whatever your father can give.
Turn to friends if you can or other family.
Conserve your precious energy for yourself.