Also there are no pieces of flesh and bone in his room, just blood. So obviously Freddy didn't "shred" or "blend" Glen.

There's no way that geyser of blood was Glen's. The human body doesn't have that much blood , not even close. The deleted body scene also doesn't explain how exactly Glen died.

He was wearing head phones so it must have been DEATH BY STEREO!!!
or else a killer water-bed that sucked him in and spit him outyou gotta watch those models- I think they were later recalled for that very reason.

The wood chipper he kept under his bed. In hindsight, not the best place to keep such a thing. At the very least, don't keep it plugged in.

The doc never sleep again shows Glenn's body coming back up from the bed, scary as sh!t, they should've left it in the movie.

Lol I love this.
The scary clown doll is hiding under my bed.

A visit from Aunt Flo gone terribly wrong.

there is a deleted scene where Glenn's body pops back out of the bed.

Um, okay. And that was on his death certificate?
What the OP is asking, I'm fairly sure, is what the police/his parents thought happened. Why was there blood dripping through the floor to the floor below? There had to be some sort of body in the room, some evidence of Glen having been there to leave the blood. Why did the cop throw up? Because there was blood everywhere? I'd think it was because he was torn to pieces somehow.

You cannot, and that is actually the point of the scene. By the time Glenn is killed, Freddy has more control than ever over waking time due to his connection with Nancy. The manual miscreant using a bed as a portal to the living world is a literal representation of how he enters in the first place which is through sleep. Glenn is pulled into Freddy's realm and the latter person converts the strength of his many victims into the most obvious physical sign of vicious death: blood. That is Freddy's way of leaving his mark. The child murderer returns Glenn's body once the bloodbath is finished. He would have no reason to keep a corpse, and doing so might even weaken his supernatural abilities since he thrives on psychological terror.

Glenn was on drugs

To be fair there are deaths in the sequels that would be hard to explain. Like the girl in Part 3 who gets rammed into a TV and there's no stool around. Also how do you explain the girl who was turned into a cockroach in part 4? Also just to add in this movie Tina's death by Rod is dubious as there's blood on the ceiling and walls indicating she was dragged. Yet there's absolutely no furniture in the room he could've used to do that. The Ceiling was pretty high. Some fans theorize that Nancy's Dad knew it was Freddy all along and didn't want to spread fear.
Green Goblin is great!

Glenn wasn't killed until he went to sleep. This was consistant how Freddy killed you.

This may sound silly but here's how I could explain it please bare with some illogic here.
You know we was sleeping with some ear phones and a TV on his lap maybe he could moved a wrong way smashed his TV's glass into his stomach and it blew up.

I admit this has always puzzled me too. What was put on his death certificate?
OMG ! LOL !! Best comment of all time !!

A giant explosive teenage bloodgasm?
That's a real thing, right? Or have I misunderstood how the human body works?

I admit this has always puzzled me too. What was put on his death certificate?

One of the greatest unsolved mysteries ever.
Lose the Game!!!!!!!

Wild animal attack?! Sorry I've been watching the earlier seasons of the Vampire Diaries too much where that's how they explain all the vampire related deaths
"I'd rather lose for what I am than win for what I ain't"
Kacey Musgraves "Pageant Material"

In this part aside from Tina in the opening scene, we only saw Nancy's dreams but in other parts this branches out to other characters although it's mostly when they are about to get killed.
"I'd rather lose for what I am than win for what I ain't"
Kacey Musgraves "Pageant Material"

I'm wondering why we didn't see any of Glen's dreams.

live near a a famous bridge, and once a man died while camping on it at night .Do you want to know the real cause of his death?
He chased a roll of toilet paper and fell off.
It's true.
What a 5h1tty way to die

Let me guess - Natural Bridge in Red River Gorge, KY?

I always wondered that too. Did they even recover a body from the deep, dark recesses of that mattress?