Looks to me as if there are two fact tables: policies and transactions, both have agent relationships. The former is SCD. The latter probably isn't. Whether broker may or may not be useful probably depends on whether that dimension has information unique from the agent dimension, or if there is a direct relationship between a fact and the broker in the source system. Broker, if it is tied to an agent, could also be SCD (hopefully, very slowly changing).

An ERD would help answer some of these questions.