Would it sound awkward if I say "in fact" instead of "actually"?
Answer from a Native speaker
I'd say this would be fine in an informal conversation! If you were to use it more formally, I'd suggest moving "in fact" to the beginning of the statement, as if you're going to give information about the "fact". In this specific sentence, I would replace "since" with "in fact" and leave out "actually". Ex: In fact, most of it takes place in September. => formal and informal Ex: ... Since most of it takes place in September, in fact! => informal use only Ex: The party didn't go well. It was a disaster, in fact. => informal use only = The party didn't go well. In fact, it was a disaster. => formal and informal