Indeed, FFP s are business companies and most are run as profit centers. But FB seems to be strongly linked to AF group and its culture.
That being said, I understand FB reaction to your querry. You are not even a client of FB and ask for difficult information. The way an agent would get an answer to your query is to access your account and see what the system says when the agent tries to make the desired booking. All responses to unusual queries are provided by the system, not by an agent with universal knowledge. They are not trained for providing answers beyond simple general rules.
You ask whether your complex itin is legal as a single open-jaw return award with stopovers. Frankly, I strongly doubt that anyone here would know. But my guess, at 99% confidence level, is NO.