One question I do have is what exactly is the importance of decision theories? [...] Are they applicable in real life situations or only in thought experiments?

One of the main functions of a good decision theory is to bridge the territory-map divide: by solving problems in your head, it shows you how to solve problems in the real world. You can identify a good decision theory when it works in theory and in practice. If a decision theory seems to work in practice, but is not describable in a precise language (e.g. "do what feels good"), it actually hasn't been well thought out and puts you at risk of being paralyzed when a very serious and very complex situation arises. On the other hand, if it only works in theory but is impracticable (e.g. "pray to Minerva for an omen"), it will be a waste of storage space in your head. In short, a decision theory should serve as a tool for you to manage your life.