OP, am very sorry for your loss & agree with u/NotFromMumbai that you should do something like Vipassana & mindfulness meditations. You don't have to do it for long but just 5 minutes a day also will help you more than immensely. It helps you a great deal. Trust me on this I am also a brain scientist as it says with my user name.
Secondly, about your career. It is very very good that you are focused with your life and career & that you care so much about your mother. It is only natural for you to spend time by yourself at Nariman Point or any other place you are mentally and emotionally comfortable with, just to get a grip on your life a little better. The mindfulness meditation will help you a great great deal with this. It will teach you to pay more attention to your self in the present.
Do not try to control the present and future, OP. Instead acknowledge that the tragic incident has happened and try to channelize your energies and thoughts on what can be done to make things better.
Your goal is to make more money so that you give your mother all the comforts she needs. So channelize your energies towards that. Take a small break of 2-3 days if you want to. Tell your mother you are going to spend time with her for these 2-3 days and inform her of your future plans. Your mom would be very proud and happy for you and that will also fill her mind with the optimism she will need to bear with the tragic loss of your father. At the same time, it will also give you a great boost in the positive sense. Cling unto it.
Also, do not think of women/ girl friends right now. Your mind is at the moment capable of only processing one thing at a time. I am positive that you will meet someone who will well and truly understand you. Do not close yourself to that. But having said that, do not focus on it right now. Right now, your main job is to be the man of the house and support your mom in all ways you can. You would be able to pull it off. And any mom in the world would be more than anticipate you to get hitched/ committed to a girl of your dreams. So do not shut yourself down and deny your mom that opportunity.
Keep plugging at your goals and hammer it down! One things at a time. Take a relevant job after your bachelors - one that you enjoy also. Because aside from the money it provides you, you would also want to spend quality time with your mom. So try to focus on that. As a back up plan do write your CAT & XAT and the other relevant management tests. You may qualify/ not qualify - but that should be a botheration at a later stage. Not now. But do give your best shot at it. It would help you to choose between multiple options & trust me that would be a great morale booster - to have the power to say no to something else.
Alternatively also look at something like a CFA/ CPA/ CA thingy since you mentioned Finance. They provide you with a good platform and also offer you good career growth.
Meanwhile, try to cheer up your mom as much as you can. Spend time with her as much as you can and give her a little space as well. See if you can take her out on short excursions - doesn't have to be too fancy- just a train ride into a nearby town just to break monotony would also be a welcome break for her.
Good luck with everything! And I am positive that you will do just fine. Remember that you need your time to cope with the loss too - so do not treat your Nariman point excursions with so much guilt. Take some 2-3 days off & break that habit of bunking college soon. Gather all your mental energies and start doing things afresh with a clean slate with renewed vigour! And also do not forget the 5 minutes of mindfulness meditation - it does wonders to your mind in ways you cannot even imagine! Good luck with everything!