Now, I am sure you said you weren't going to try writing, sorry, publishing your work until you had grasped the basics of language, but I will try and offer some advice.
On the whole, you have extended your analogy/metaphor far too much in such a short passage and it only serves to confuse. On first appraisal, I struggle to understand what you are trying to describe or talk about.
It was just an old door Peter stood behind.
Clumsy sentence as I think Hugh pointed out. What about "Peter stood behind an old door" or even put the 'that' in that your sentence desperately asks for.
A plain old door with a faulty knob and a squeaky hinge. But to Peter it was a curtain that draped down heavy.
Draped heavily or draped down heavily. Not heavy. This isn't Woodstock. And the draping doesn't really relate to the door, a thick heavy curtain sure, but the mention of 'draping' confuses your comparison.
A curtain that he opened slowly before taking a hesitant step forward. For the hot spotlight, high up the stage, beamed bright his every move.
Grammatically the addition of a new sentence beginning "For..." isn't good. Use a semi-colon or rework your sentence. I am sure I have mentioned before that playing with grammatical rules is ok if you are a skilled writer and you have the talent to make a point or just for fun.
Peter didn't dread the curtain, the stage nor the light, he feared being unearthed by the audience as a fake – a performer who could not persuade them with illusion.
I am confused here. Was the curtain a door? Or is that a continuation of your comparison? A curtain makes logical sense with the stage and the spotlight, but from what I know of theatres, very few have a creaky door that lead onto the stage. Or is the spotlight and the stage a further comparison for something else? In which case you have taken your comparison too far and rather than make your idea vivid you have just cloudied everything.
With a single blink, the curtain was gone, erased by expectation.
Now I am lost. Expectation of what? A performance or just walking out into the urban landscape?
Peter closed his eyes, took a deep, soothing breath, opened his eyes and walked outside: his eyes crimson, teeth clenched just slightly, fists loose, sway, relaxed and slow.
Crimson eyes? Is this in-keeping with a character you have created?
"sway, relaxed and slow" is awful, just plain awful. Do you mean his stance? That he is swaying?
For the slum that was the inner city was savage. It's actors, unmerciful and swift.
You have taken your metaphor too far and I am really confused. The actors are people in the city?
The best advice I can give you Pontiac, apart from the glaringly obvious, is to stop trying to be wordy and intellectual. Do you use sentences beginning in "For..." in your everyday speech? Try and sound natural, stop trying to sound wordy. I feel that you are tying yourself in knots trying to be somebody that you are not.
