I could be wrong, but I think you can avoid Eric getting anywhere with all of them except for Ann if you wait until after you get rid of Eric to put a web cam in Alice's room, help Lisa with her homework, or do anything with Kira in the shower.
If I'm not mistaken, Alice's blog event series doesn't start until after you put the web cam in her room, Sex Ed lessons with Lisa aren't triggered until after you help her with her homework, and Eric doesn't do anything with Kira unless he catches Kira sucking Max's dick in the bathroom. So counterintuitively it seems like the best option on the war path is to intentionally NOT make progress with anyone until after you get rid of Eric.
From what I've seen, Eric's Sex Ed lessons with Lisa, his perving on Alice during her blog, and him getting some from Kira are all unavoidable if you trigger any of that stuff before getting rid of him. His progress with Ann is unavoidable no matter what you do.