Whoops, I missed some stuff in your original response. For the default characters, check the FAQ I added yesterday at the top of this page.
For project classes, once a week is generally fine, I believe a few extra times is needed for harder classes.
The stat gate specifically tunes whether this line is injected or not: "<Name> isn't attracted to the reader yet. He needs to be more <stat>. <Name> won't make or accept romantic advances."
So it's generally a lot easier once you hit the stat barrier, but of course still possible to get with someone before.