How can one deal with a father who is stingy, ill-tempered, quick to anger, unemployed, insults the mother, and neglects his children, while the son tries to adapt to the situation and shoulder the financial responsibility?

It is not permissible to be harsh with a parent, no matter how much wrong he commits. Rather, he must be advised and reminded gently. You will be rewarded for patiently enduring his harshness and for honoring him. Financial support for him is obligatory if he is poor, and commendable if he is not. The father is obligated to provide for the mother and to refrain from being harsh with her; this does not justify his disobedience to his parents. One should not travel far from him, and it is better to patiently endure his harm, for there is a reward in it, and Allah will bring ease after hardship.