I think we are like our Mother's there whether we like it or not.
You could walk around my Parents house and not find a speck of dust anywhere, any day. I used to think she was obsessive in cleaning, alas, i picked up the same traights, not as bad, but loosened up alot as i got older, one because of the heavy work committments and two because life is to be enjoyed and you can't spend the whole time cleaning.
If you are moving in with your man in August, then i would be saying that there has to be a bit of slack there.
If he was bought up in the household you describe, that is what he is accustomed to. Leaving toilet seats up, we leave them down, ( now about that who's right/wrong?) No one as we are equal one likes it up for usuage the other, down,
But if you do feel the need to "place your shoes there because, do this because, don't do that because", it may come across as nagging as well, so if you carry the cleaning to this extent then have a think there.
I received an email the other day about handbags and it floored me really, as we do, we put it down on the floor of the toilet ( well i do try to hang it up when there's a hook) and we know what goes on the floor of toilets, etc.
I would have difficulty eating in his parents house to be honest, but apart from that, i would be okay. I too like a clean house but i sell them, so i see all sorts i guess but i know the amount of times, i have said no thanks for that coffee or glass of water...ahhh....
I truly don't know how you can handle that one other than when you guys live together try to always have the invite to your home for meals and then of course, your going to be asked "can i help?" So, it's a tough one....
CW