6 and 10 for the Durgetash asks?
answering these :]
6. Describe their dynamic in one sentence. Without using toxic.
Annoying coworkers with absolutely no boundaries whatsoever are playing mindgames, but only one of them knows the rules (and it's not Aeres)
10. Did the tyrant ever try to impress the serial killing godling and exact how horrible did it end for him? What sorta things did he do solely for 'the sake of cooperation' with glaringly obvious ulterior motives?
He tried. When they first met, they were not on equal footing: Aeres was a few decades older and already established in her growing cult and worship and Gortash was still the grimy arms dealer with grand ambitions that cast mostly hollow shadows. The Bhaalspawn was unimpressed and would continue to be so for quite a while. Any attempt at personal flattery was disregarded and any gifts to her cause (be it bodies or gold) were merely accepted- but did not change the status quo. There weren't any horrible consequences bar a dead courier or follower here and there.
He did impress her with how he achieved his goals, climbed the social ladder and followed his ambition. The moment she considered him an equal in their alliance thanks to those was also the moment she started seeing their shared worldview and traits. That kinship was a first for her so she sought out more and Gortash was perceptive enough to notice. A few years in, he found the winning strategy of twisting his ambitions and projects into joint efforts: His seat on the table of politics to open the city’s doors for her assassins. His Steel foundry and tin men as efficient automated murder machines for her visions of mass extinction and so on. A shared nature, a shared dark path, a shared end to all of it. Those were a lot harder to disregard.