Dennis is funny because Macs tried to heal a relationship outside the gang (his dad) but it failed immediately (rejected, unfair) and Charlie's done it too, even planned to leave, but also failed straight away (loser father up and died on him) and Frank doesn't want to leave, and Dee is not permitted to leave (not even to go bowling! they need their punch bag!) but Dennis has actually been out there. He's gone and tried it. He invested in a life outside of Paddy's Pub, he left and tried to go be a dad, be a better person than Frank was, and... it did not fuckin work! Couldn't do it. Came crawling right back after being gone for months. Which means he's the only one out of all of them that knows for sure there's nowhere else to go. None of the rest have really tested it—it's just a pipe dream for them—they can imagine it however they want! And that's a pretty useful psychological pressure valve. Their own places in the gang are inherently lower stakes for them because they can still believe if it all falls apart they'd figure something out, they got plenty of other options, definitely. They may worry there's nowhere else for them, sure, but you know what you can do with a worry? Move past it. Except for Dennis. Who knows he can't afford to rock the boat, or deviate too much from his assigned role, i.e. still very much the "leader" of the Freight Train, still their new psycho, even if he is a little mellowed with age. So he left because he wanted to quit all the delusional bullshit, wanted to try something real. Then found out "real" didn't want him in it. And came back to the gang, and for a little while he tried to make a change: The Gang Escapes, "let's keep this between us"; Times Up, "I don't want you kissing me" + [extensive instructions in how to not get caught]; Even up to New Wheels he's trying something new, til he embarrasses himself in front of Frank. Til fate hands him his old car back. And if reality don't want you, you're not gonna say no to fate, are you. At least he's got a place in the world. At least somebody wants him around, some kinda way. It's good actually. Who cares if it's not who he really is. He knows there's nothing else out there. The others don't, but he does. So he can keep his secrets, play his part, don't dwell on it, it's cool. It's whatever. After all it's not like you can just "move past" reality, can you. Can you?