"Ultima IV, it was the last of the turn-based / square-based Ultima games"

Historical quibble. V used the same basic engine as IV. VI (and the two "Worlds of Ultima" spin-offs) had an upgraded engine, but was still square-based, and largely turn-based.

"whether or not you murdered *too many* innocent little girls, where "too many" was, inexplicably, a number greater than zero"

This was a matter of some debate among the team. The eventual decision was that most players, even 'good' ones, would want to see what happened, so they got one 'gimme'. But if you did it again, after seeing what happened the first time, you got the bad ending.