Dear Problems Prioritizing,

For your first question - one good way to go about figuring out what you REALLY want is to think: "what will I regret if I don't do it?"
If you do not travel now, before you are married and settled, will you regret not going? Will you ever have this opportunity again? Also, if your boyfriend is away for an extended period of time, maybe this is the right time to go away. There are many clichés that would work here (for example: distance makes the heart grow fonder).
Three months of time is not terribly long (in the whole scheme of life), both family and friends (and boyfriend) are probably unconditional relationships that would want to support you in all you do.
As far as marriage and being settled, is your boyfriend also considering that right now? If he is away from you at the moment, how will a marriage work? Assuming he is on the same page, do you think you may resent him later if you do not take the time to travel now?
As far as your second question - have you been away from family and friends before? If not, maybe it is a smart idea to do something independent before settling down. When people find themselves in situations that they are alone and far away from loved ones, you will find that you end up stronger in the end - and most likely have an amazing experience.
Regardless of what you decide, just make sure you won't regret your decision. Life is too short for that!