Going off and leaving the house unsecured is a "little thing" ??? You must live in a very low crime area!
People remember what they want to remember and make a strong effort to remember. If he's not willing to pay attention to your comfort requirements, to make personal changes meet those requirements, then he doesn't want "a relationship" he just wants "company".
In my marriage, I had to make a choice between either putting up with a fellow who, after 10 years of marriage still hadn't learned to re-close the toilet lid ... or to give him an ultimatum. I gave him the ultimatum (you have 90 days to show marked improvement), he kept right on leaving the lid/seat up, and I moved out of the house. A year later, we filed for divorce.
Yeah, you're saying "She divorced the guy over leaving the seat/lid up?!!??!?" ... But it wasn't the seat. It was his refusal to make even this small personal change for the sake of pleasing me.
Make some small ultimatums first, so he knows you aren't bluffing and really mean it. Escalate to "... or I'm leaving you" if you think it's worth it. Don't make ANY ultimatums you aren't ready to stick to, because you will probably have to carry many of your threats out.
BTW, I have been with my current guy for 5 years, and I've never felt a need to nag about anything ever. I ask only once "Can you use the blue mug for your coffee? The white mug is hard to wash" and I never have to mention it again. This man CARES for me.
PS. Don't let these people guilt-trip you about nagging. They are trying to cover up the fact that it is YOU who are the injured party here. You should not be put into a position of reminding a grown man over and over about the same thing.