I just finished it. What really irritated me was why the heck did he write the part where seven 11-year olds had an orgy in order to find the way back from the sewers. What. The. Fuck. Stephen. WTF.
And IT was definitely female. The discovered it was pregnant when they fought it as Kids. By the time they came back to finish the job 27y later, IT already laid some juicy spider eggs.