There is actually some amount of fact relating to Mark's personality in the flashback here, gained from http://www.wrestleline.com/columns/monk/oct99/monk10899.htm   However the rest is probably way off.
 
Title: Until It Sleeps (4/?)

Fucking wheelchair.  They couldn't find one to fit me, but they insisted on wheeling me out of here anyways, so I've got my knees up in my fucking chest cuz the chair's too small.  Of course, Dennis just keeps talking and talking.  I haven't gotten a moment of quiet in days because he never shuts up, just keeps babbling.
 
And finally, we're going home, back to Texas.  The doctors are making me take a while off wrestling still, to heal up and make sure my brain doesn't fall out of my head or something, so I'm planning on just relaxing on my vacation.
 
Vince gives Dennis more time off, supposedly to take care of me.  I don’t need a damn baby-sitter….but there's a little voice saying that it's good he's not going back yet, that this keeps him safe from Helmsly and McMahon until I figure out what's going on.
 
Except Dennis won’t leave me alone.  Ever.  He's like a little puppy dog, following me around.  And still talking all the damn time.  And I can tell he's getting bored, because he keeps wanted to DO things.  Play Scrabble.  Watch movies.  Hell, one time he asked me to play Twister.  I can’t even bend my knees, how the hell does he expect me to play Twister?
 
And now he's pulling out tapes of my old matches.  And some of them are REALLY old.  Now we're on one from way back, back when I trained with the Von Erich's.  I see Kevin Von Erich do an elbow drop, hear him yell something at me, probably to move quicker or change my focus…
 
"Dammit Callaway, I know he's shorter than you, but not by that much.  Would you please look up for a moment?"  Fritz Von Erich yelled from outside the ring where Mark and Fritz's son Kevin stood.
 
Mark glanced from where his eyes were glued to the floor.  "I'm sorry."  Back down to the floor they went.
 
Fritz sighed.  "Mark, I don't know what your problem is, but I can't teach you anything if you don't look at him."  His voice got gentler.  "He don't bite, kid."
 
"I know."  But Mark still wouldn't meet Kevin's  eyes.
 
Fritz closed his eyes in frustration.  "Alright, how about we work on some holds?"  He called out to Kevin, "Show him a hammerlock…" Kevin moved behind
Mark, grabbing his wrist, twisting it behind his back…
 
And the next thing Kevin knew, he was lying on his back.  Mark had backed up to against the ropes, his arms wrapped protectively around himself, his eyes wide with panic, his breath coming in hard gasps.  Kevin jumped up immediately, getting up close to Mark.  "What the hell are you trying to pull?  You can’t just fucking jump me like that!"
 
Fritz took a deep breath.  "Relax, Kevin."
 
Kevin whirled around to look at his father.  "Why?  The fucking rookie just hit me!  How the hell are we supposed to train him if he keeps doing that?"
 
Fritz climbed up into the ring.  "Drop it.  Why don't you go hit the showers?"
 
Kevin stared at him for a moment, then left grudgingly.  Fritz walked over to Mark.  "You ok?"  Mark nodded, keeping his head tucked down.  Fritz lay a hand on his shoulder.  "Something you want to talk about?"
 
Mark looked up, his breathing still shaky.  "No… it's just a reflex… I'll do better next time…"
 
Fritz patted Mark's arm.  "Why don’t we call it a day?  Go home, get some rest…"  He walked away, leaving Mark standing alone in the ring, still shaking.
 
 
"Mark?  Mark?  Hellllooooooooo???"  Dennis's voice broke me from my thoughts.  "Come back to me Mark, don’t slip away into a coma again.."
 
I swatted at Dennis, watching him grin.  "Damn you…can’t you let me sleep?"
 
Dennis tilted his head.  "Unless you sleep with your eyes open, then you weren't napping.  I bet you were reminiscing."
 
I glared at him.  "No I wasn't."
 
"You were so!"  Dennis laughed.  "I think you were thinking about your glory days…"
 
"I had glory days?"  I pulled Dennis closer to me without really knowing why.  "I didn't know I had glory days…"
 
Dennis rolled his eyes as he leaned back against me.  "Oh come on.  You've had the belt a million times.  You got to scare people on a daily basis.  Tell me that's not glory."
 
There he goes again, talking like he thinks I'm special.  I guess some things never change, no matter how long you're out of commission.  I hate it when he does this whole hero-worship thing, because I'm not who he thinks I am.
 
But for now, he's fallen asleep.  He's kinda cute to watch, his head resting against my chest.  Absently, I ran my hand through his hair, playing with the curls.  He moved closer to me in his sleep, his hands clenching in my shirt.  I wrapped my arms around him, and his grip relaxed slightly.  And we sat there, in the dark room, the flickering TV the only light.  I tried to sleep, but my back hurt and I didn't want to wake up Dennis so I could get up and grab my pain pills.
 
So I just watched him, his slow, deep breathing, the way his eyes fluttered.  And for a moment….for a moment it was truly peaceful.