Hello from JustAnswer.
Some of your questions are clearer than others, so let me first address the questions that are clear.
It would be impossible to know what your friends want until you ask them.
Some people simply want someone to listen and to whom they can ventilate their feelings. In that case, all that is needed is for you to listen with compassion.
Other people that are facing difficult decisions may be seeking your opinion on the pros and cons of each decision. Being able to discuss each option considered in the decision making process can help them get to a better level of understanding so that they can make a better decision. In this situation, you can help by being able to offer a new perspective on each option.
When someone has approached you and discusses a difficult situation, it is appropriate to first listen, and as the discussion progresses, you can ask them how you can help.
As for whether you should walk away, that is a personal decision, but it sounds like you care deeply about these friends and situations, and it is usually better for someone that cares this deeply to continue to try to assist to the extent possible, rather than walking away.
However, it is also true that the additional emotional strain from friends that are in difficult situations can also place a toll on you. And if you are feeling personally anxious or depressed because of this, it is important for you to also look to your own mental health. If you are feeling more anxious or depressed, it may help for you to seek care for these issues, either with counseling or medicines that can help ease these symptoms.
Is this the information that you are seeking? Or is there additional information that would be helpful?