For #2, reading (https://www.fanfiction.net/u/443241/reading)'s Strangers and Angels (https://www.fanfiction.net/s/2748108/1/Strangers-and-Angels) story has Sam nitpicking on Dean's design drawing and making his brother feel bad without really realizing he was doing it.
And for #3, since you said sexual abuse is okay too..but just to warn you, this is REALLY...like really messed up lol. A Fine Caliber (http://archiveofourown.org/works/948804) by aspenspark (http://archiveofourown.org/users/tempusborealis/pseuds/aspenspark) (non-con, John/Dean, Sam/Dean, Dean/dogs...puppy play, just a lot of weird stuff so yeah read at your own risk) summary: It was when he was fourteen that John decided Sam was old enough to have the dog he’d always been asking for. Of course their lifestyle didn't really allow for pets, so they’d made do with the next best thing – obedient little Dean. John just can't resist showing him off and teaching a somewhat reluctant Dean just how perfect a bitch he is.
I also recently discovered this awesome series (I never got into abusive!John but eh exceptions are made for everything). Birds of a Feather (http://archiveofourown.org/series/81574) by bluetoast (http://archiveofourown.org/users/bluetoast/pseuds/bluetoast) (blind Dean, abusive/neglectful John, Adam, Sam, OCs)
when my soul invites you in (http://archiveofourown.org/works/1032744) by Mekina (http://archiveofourown.org/users/Mekina/pseuds/Mekina) (abusive!John, John/Dean, implied Dean/OMC, Dean/Sam) summary: Nine years ago, Sam saved Dean and was taken away from him. Now Dean is back, and he's there for Sam.
Not sure if this really counts as abusive since in this series, Dean was caught and turned into a skinwalker and when John and Sam sees Dean after years (he was kidnapped when he was a little kid), they didn't know it was Dean...they kinda treat him poorly, chaining him in a motel while they're out and all that. But it's really good. Skinwalker!Dean (http://archiveofourown.org/series/15418) verse by liliaeth (http://archiveofourown.org/users/liliaeth/pseuds/liliaeth)
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And for #3, since you said sexual abuse is okay too..but just to warn you, this is REALLY...like really messed up lol. A Fine Caliber (http://archiveofourown.org/works/948804) by aspenspark (http://archiveofourown.org/users/tempusborealis/pseuds/aspenspark) (non-con, John/Dean, Sam/Dean, Dean/dogs...puppy play, just a lot of weird stuff so yeah read at your own risk)
summary: It was when he was fourteen that John decided Sam was old enough to have the dog he’d always been asking for. Of course their lifestyle didn't really allow for pets, so they’d made do with the next best thing – obedient little Dean. John just can't resist showing him off and teaching a somewhat reluctant Dean just how perfect a bitch he is.
I also recently discovered this awesome series (I never got into abusive!John but eh exceptions are made for everything). Birds of a Feather (http://archiveofourown.org/series/81574) by bluetoast (http://archiveofourown.org/users/bluetoast/pseuds/bluetoast) (blind Dean, abusive/neglectful John, Adam, Sam, OCs)
when my soul invites you in (http://archiveofourown.org/works/1032744) by Mekina (http://archiveofourown.org/users/Mekina/pseuds/Mekina) (abusive!John, John/Dean, implied Dean/OMC, Dean/Sam)
summary: Nine years ago, Sam saved Dean and was taken away from him. Now Dean is back, and he's there for Sam.
Not sure if this really counts as abusive since in this series, Dean was caught and turned into a skinwalker and when John and Sam sees Dean after years (he was kidnapped when he was a little kid), they didn't know it was Dean...they kinda treat him poorly, chaining him in a motel while they're out and all that. But it's really good. Skinwalker!Dean (http://archiveofourown.org/series/15418) verse by liliaeth (http://archiveofourown.org/users/liliaeth/pseuds/liliaeth)
I might have more somewhere. I'll have to check.