There isn't any specific advice in the Qur'an and hadith about this, apart from the general advice that it is good to have a profession.
However, you could consider what types of things you enjoy doing and come easily to you, and also what skill sets are easiest for you. (For instance, are you good at working with your hands, art, people skills, mathematical skills, etc.)
It is also good to ask other people for their advice since they may see things in you that you are not paying attention to.
If you have the opportunity, you can also try different things and see what does or does not suit you. Every master chef begins with the first dish! The difference between the master chef, and the person who quits and does something else, is that the master chef perseveres.
Sometimes people do multiple things in life (at the same time or at different times), so you do not always have to choose one thing.
Also, people are often quite successful in jobs or endeavors that are not really their "true passion" or their best talent but are simply something they began to do or had to do. Possibly this is because when something does not come naturally to us, we have to work harder to get good at it, and, in the end, someone who works hard to learn a skill will do better than someone who has natural talent but who does not work to develop it. Most people can do most things with training and effort.
You can also consider what is important to you, how you would want to be remembered after your life, or if there is any particular group you want to serve. For instance, some people go into Islamic religious work because they want to serve the ummah, or feel a similar calling. Some people go into medicine because they want to help people or see a need for it. Some people go into business because they admire people who are successful at business or want to provide a certain product or service somewhere, or help a certain community economically.
With duas for your success!
I am sorry to hear about your difficulties. You are not allowed to end your own life, and this is a firm prohibition in Islam, since life and death belong solely to Allah.
Sometimes people end their lives because they feel that they have no way out of the difficulties they are facing. If that is your situation, it is good to pray that Allah opens some doors and finds a new way for you to improve your situation. (I am sure you are doing this, but you can continue to do it, inshallah.)
You also do not know what Allah has planned for you in the future, and maybe you have some things that it is important for you to do in the future in life, and you will look back and realize it was important for you to continue living. So right now your job is just to get through your situation in the here and now.
As they say, it is often darkest before the dawn, and difficult times do not usually last forever. Oftentimes, Allah's mercy reaches us when we are at our most difficult point and then we find relief from whatever we are suffering from. So do continue to pray for assistance and have hope!
Yes, it is permissible.
It depends on your body condition. Exercise is good as far as it does not harm your health and does not take very long to waste your time. Every person has his own limits which he feels.