I must be doing something wrong ...

[LIFEphemeral]

I just wanted to clarify if I was translating this correctly, because it confused me a bit with the ｘのｘのない

疾走する悲しみが せつないの
実態の無い うつりゆく未来へ

The sprinting sadness projects itself out to the painful future without truth? (I'm not using the backwards way of speaking that she did yet).

Whats the significance of the の　after せつない？ I feel like I'm missing something here.

Edit: For a while I thought it might be a question marker, the no after setsunai, but then I found another no used as a question marker and a question mark followed it so ... is it a feminine exclamation point?

That makes the next line a fragment though ...
 

[Yumitoko]

の = no = it's a particle.

here.

http://www.timwerx.net/language/particles.htm  

[Yumitoko]

no= is a possessive particle.



mary-san no
miss marry's  

[Maboroshibito]

の is commonly used as a possessive particle, however...

You were right. It is an informal way of marking a question.
Note: In 日本語 questions marks were not used to begin with. Only in recent and modern publications, etc, are question marks implemented but not mandatory.

And also, your hunch about feminine use is somewhat correct.
However, it is not as much an exclamation as よ。 For females to use this, it is more like emotional emphasis.

It can also be used as a conclusion of confidence in a statement.

Hope this was helpful.
がんばってください～  

[=X-Sparker + AquaKiller=]

I agree with Vorkudlak.
I would translate these two sentences as:
Is the sprinting sadness painful?
Towards a passing future without reality.

Question mark is not required to be placed after の
to make it a question. So the first sentence is pretty
obvious a question.
Rather, I have a question with the second sentence.
I translated it as "Towards a passing future without reality",
but since you mentioned she speaks backwards,
then it's possible it can be translated as,
"Passing towards a future without reality".

Hope that helped. Good luck!