1) Keep going to hearing, keep going to afternoon meetings, eventually she should suggest that you have lunch with her. Depending on how far you have progressed with her, you can visit her on weekend morning (in her office), this can lead to some more spicy stuff. At some point you will learn that she has parties twice a week in the evenings, if you can get booze, you can get entry.
2) If you attendance is suffering, you can just make nice with the principal and get her to fix your attendance, at first you should do the task she gives you as she says, after a few tries, be a little rebellious and show off, that should fix any issue you are having and should progress with the principal
3) To progress with Mary you have to back track some times to advance, try going back to kissing and she will but with progressively fewer clothes. If it is Alexa you are having issues, you need to progress with Mary to invoke Jealousy, but helping her get off and taking pictures should help.
4) So far there have been no negative side effects from it, but it is extremely lucrative and opens up sex option with the bank manager. So I guess it is up to you.