Op, I suspect that you're partly complacent about this bloke because you've actually known him from when you were children am I right? Except that now that dynamic has changed and as such your boundaries are out.
Ultimately the most important element in any relationship or even potential relationship is communication. If you can't communicate effectively then you have no way of being able to move the relationship forward to a point where you are both in the right place iyswim.
My now DP was originally a friend, and after my marriage ended we caught up as friends. He came to stay here, there were never any expectations because we weren't heading in any kind of direction iyswim, but as it turned out we just clicked and ended up getting together. When he left here (he lives three hours away from me) I said to him "don't drop off my radar. If this is going to go anywhere then you need to keep talking to me. I am a born communicator. He on the other hand can be lax at it, and there was no way I was going to chase communication from him, so I laid that one out from the outset. Had I had to remind him of it then tbh the relationship wouldn't have gone anywhere. I am not up for that kind of anxt over non texts etc so it wouldn't have worked for me. But he didn't ever need reminding. :-)
Don't over think things. If he's inconsiderate work out how far you're prepared to put up with that. Only you know whether you feel that you're safe staying at his. By safe I don't mean that you are at risk of harm (although obviously you have to be sure but as you know his family this isn't the second time you've met this bloke). but safe from expectation. My DP stayed here when he visited because we live so far apart so there wasn't an alternative. But I would only have agreed to that in the knowledge that he didn't expect anything until we were both ready iyswim. If you think he may have expectations or if you think he may try to move the goal posts then make sure you're comfortable with that, don't be held to expectation just because you've agreed to stay over.
Nothing wrong with having a drink, but everything wrong with using drinking as a reason for staying with someone you think has the capacity to break your heart. Alcohol lowers your inhibitions especially if you're an infrequent drinker...