No worries, that's not happening. He tries to "teach" Lisa and the worst you get to see is her seeing his dick. First time you can't prevent that by enterting the room unannounced, but she won't like that very much. After that you can buy something from the internet to drug him before dinner, so he either spends his time in bed or on the toilet.
I think you do have to catch him once with Ann, so Max gets a certain idea, but I am not sure about that. I don't care if there are other chars involved ot not (I am more focused on the story), so I didn't try to avoid it.
He will try to get into Alice's pants as well, by buying her stuff, so you need to beat him. However, so far he won't be successful, even if you are too slow. But she will show the sexy lingerie to him and not to Max.
No, the game is not NTR focused at all. You compete with Eric, but so far he didn't have any interaction with anyone except Ann. If you are on open war path and he catches you with Kira at night, then yes, she will have to blow him at night (which you don't need to see, most of the time Max will be asleep anyway). The simple solution: Don't meet her at night until he's gone.
