Will was successful with teaching Brittany the alphabet, so maybe he and Emma will stumble on better ways to tutor Brittany. Whatever Brittany has, it's not a developmental disability I recognize, but I am no expert. As I've said before, her version of what's going on is different from the consensual reality that Artie, Kurt and Santana had together. She passed for ditzy, but not really with Kurt, who said that she thought the square root of four was rainbows. I can't do square roots either. I wished many a time for there to be a Happyville where math hadn't been invented. I flunked algebra the first time, and got through it the second time with a tutor. Of course Mom thought I was just being lazy the first time, but I think I had learning disabilities that weren't diagnosed.
Kurt saying that he'd get people to leave him alone when he went out at night by twitching and yelling at things was a good strategy, in my opinion. We've had it emphasized for three seasons that everyone who sees and hears him assumes correctly that he's gay. Coming across as effeminate in a rough neighborhood isn't safe, but pretending insanity (or being in withdrawal) would distract observers. There's such a stigma around mental illness. Twitching is a side effect of being on any of several meds, or having been on them for a while. Yelling at the invisible or inanimate is another symptom of certain mental illnesses that's known in popular culture. (Added: Kurt specifically said he would act like a "crazy person.")
Probably the main reason that Will will fail with communicating with Jake is Will's racism. I thought Puck would say something about Jake being biracial, but I don't remember him doing that. Will thought better of Jake when he learned that Jake was half-white. Puck just accepted Jake as being his brother, and Puck said how their father being a deadbeat had damaged Puck. That's probably some of Jake's damage, too, but that's likely not the entirety of it. If Blaine is ever established as being "hapa," Will will think less of him. That's how Will is. Will doesn't want to be friends with people who aren't white.
Jake was quickly established as flirting with all the girls. It wasn't developed like in Puck's voiceovers about "cougars," but it was clear enough to Unique. Unique led the song. As Calanthe pointed out, Jake didn't hear it. I found a looped rope being dropped over Jake's head and shoulders when it was established that he was flirting with the girls to be quite unnerving. It was a bit too much like "the strange fruit that hangs from Southern trees" for me. Maybe it's what I've been reading lately.
I noticed that Sam's map for Brittany included the directions "Meet me hear" (sic). I wonder who will notice about Sam's grades. Sam is aware that his grades aren't good because he's dyslexic. That was established with him right away, and then not spoken of again. His getting the word wrong may be an indication that that will be picked up on again.
So Britney 2.0 had various kinds of developmental disability and a pretense of mental illness. I thought it had some content about racism, too. I'm very curious to see who picks what up with Brittany and the way her brain works. Sue drew her a picture of the cannon and its baby cannons, and told her a story. Brittany was disabused of the belief that Rory was a leprechaun. Brittany has been established as not tolerating it when people call her "stupid" or "an idiot." "Idiot" and "moron" were once official classifications before they fell into just being slurs about mental ability. Now I'm associating that with Terri using the word "Mongoloid" before characters with Down Syndrome were introduced on the show. Terri was just awful, though. Scientists at the time "Mongoloid" was coined put a high emphasis on a connection they saw between epicanthic fold and intellectual ability. Some racist stereotypes have changed in the U.S. since then. Stereotypes about developmental and intellectual disabilities (and mental illness) haven't changed much, though the names used to describe them have.