Furthermore is an adverb that is used in a sentence to introduce a new idea in an argument. It also serves as an adverbial conjunction.
An adverbial conjunction can be defined as a conjunction that is used to join two main clauses or independent clauses. It is used to shift from one idea to another without interruption.
In the given sentences, the word that can be best used to join two independent ideas would be 'Furthermore.' It is because the two sentences are independent clauses and the two ideas are presented. Thus to swiftly shift from one to another without interruption 'furthermore' adverbial conjunction would be used.