The Unit 3 Individual Project is guided by opinion, and therefore I had addressed the areas required by assuming that I was a manager at Blue Mountain Company, and ethically handling David Tuff's situation.

The Unit 3 Individual Project is guided by opinion, and therefore I had addressed the areas required by assuming that I was a manager at Blue Mountain Company, and ethically handling David Tuff's situation.

Does this HAVE to be one sentence?? And what is the point of that past perfect verb in there!!??

Here is how I'd rewrite it:
The Unit 3 Individual Project is guided by opinion. Therefore, I addressed the areas required by assuming I was a manager at Blue Mountain Company; I also handled David Tuff's situation ethically.

??

Or ...

The Unit 3 Individual Project is guided by opinion; therefore, I addressed the areas required by assuming I was a manager at Blue Mountain Company. I also handled David Tuff's situation ethically.

=)

Yes, it does not necessarily have to be one sentence. You have provided two variations of rewriting the sentence, both of which are grammatically correct. The purpose of the past perfect verb "had addressed" in the original sentence is to communicate that the addressing of the areas required by assuming the role of a manager and ethically handling David Tuff's situation had already taken place before the statement was made. However, using the past perfect tense may not be necessary in this context, and using the simple past tense as shown in your rewrites is perfectly acceptable. It is important to note that different writers may choose to express the same idea in different ways based on their writing style or preferences.