I'm coming here really late but I hope you read this and hope it helps.
It feels to me he was definitely fast asleep and passed out drunk and reflexively reached out feeling (or dreaming) he was sleeping next to his wife.
However, you should NEVER let a drunk adult whether male or female sleep next to your small child. Like what in the actual f.... Even if we forget about possibility of sexual harassment/assault, it can still happen that the person kicks you, hits you, rolls on top of you pukes or defecates in bed. I think you should actually confront your parents.
And about that guy, if you never felt that kind of weird scary energy from him afterwards (and I don't mean smiles) like inappropriate comments, attempts to touch you or be alone with you...that kind of behaviour that just gives you that feel in your gut, then it's likely that he's not a sexual harasser or paedo, but if it would give you a piece of mind just tell him "you remember that one time you stayed over at our place drunk...well you did so and so and I'd never bring it up but I can't shake it off so many years later" and measure his reaction.
I can't see the reason that your parents allowed an adult male to sleep in a little girl's bed even if he had "little ones" of his own - that's not a REASON to allow an adult to sleep with a minor. There had to have been a couch he could have slept on - he could have even slept on the floor. And just because he was snoring doesn't mean he was actually asleep - I mean, he smiled at you later and called you by a nickname that HE picked out for you - to me, that says he was aware that he had done something wrong.
I would say that, if you feel strong enough to confront him, you should do so but know this - he will deny it and may curse at you; he may ask you why you are bringing this up after all these years; he will try to make you feel guilty about it - telling you that you liked it because you didn't tell your parents back then.
If you choose to confront him, do it in a public setting as he might get violent and hurt you. And be prepared for him to get LOUD and embarrass you..
Hey, I'm sorry no one ever responded to you. Such a sad thing to have a memory like this unresolved. It could have been a dream. It could have been him sleeping and not realizing (why your parents would put a grown man in your bed is beyond me, that's highly inappropriate. Especially a drunk one, geez). Or he did something. That's always a possibility but you never heard of any other allegations against him, correct? Which makes the first scenario or the second (not okay but not an intentional assault, just horrific judgement of your parents) just as likely. You may never know. I think I'd choose to believe scenario one for your sake but if you can't choose scenario 2. Also, you could talk to a therapist about it to get the feelings out and guidance. Why would you be disgusted with yourself over something that happened when you were 5 years old? You weren't a cognizant adult yet.