He's in the pretend friendship path. I played the same path. You can buy and use drugs to prevent Eric from having one on one with Lisa every Monday night. It's a temporary solution to stave him off until you're ready to interrupt him.It seems that you are already at the war path, because I don't think the bath event happens on friendship path.
Once Eric starts lessons with Lisa, Max will get the idea to look for drugs on the internet.
The 'kick Eric out' event will take place automatically at some point. There is nothing you can do about it.
Use the time to advance in the schoolmate opportunity and try to get two different pictures of Eric outside and inside Alice's room (first one outside).
Because currently there is a design flaw, you can't proceed on schoolmate once Eric is gone (because Ann is always at home then).
This part I'm not sure since every time Eric catches me and Kira fucking, I just load back and choose to cum early to prevent being caught. So yeah, I was able to rid of him without him touching any of the girls except Ann. In your case, maybe talk to Kira about it, watch Kira and Eric fucking in the evening (and peek at Ann alone in the bedroom while they're at it) then talk to Kira the next day... I don't know maybe there will be some triggers. There's nothing in the walkthrough that says you need to do something to move forward on any op if Eric catches you and Kira fucking.There's no way I can start a war with him. He doesn't talk to me after he caught me and my aunt in the bathroom
War with Eric will start after you interrupt his personal lesson with Lisa on a Monday night. For that to happen, Lisa will talk to you at one of the after dinner times about Eric convincing her to have one on one lesson with him. That will happen after you watch Eric and Ann's lesson with lesson with Lisa (and talk to Lisa afterwards during homework) many progressive times.