in between, wicked and wild, an empty I.O.U - what do they mean?

[Anna.ha]

Hello,

Could anyone explain to me what those words mean in this context

I figured it out
I was high and low and
everything in betweenI was wicked and wild, baby,
you know what I mean
Till there was you, yeah, you

Something went wrong
I made a deal with the devil
for an empty I.O.U.
Been to hell and back, but an
angel was looking through
It was you, yeah, you
It's all because of you

Thank you!

[Mister Micawber]

.
These are just song lyrics and do not necessarily mean anything.

everything in between -- at all positions/feelings/etc between (high and low)
wicked and wild -- evil and unruly

I made a deal with the devil for an empty I.O.U. -- I did bad things and received nothing in return.
.
_________________
Native English teacher at Mister Micawber's

[Anna.ha]

Thanks Mr. M. Could you please tell me what I.O.U stands for ? I've searched it on the internet and there are quite a few acronyms, I dont know which among them should be used in this context.

[Gray]

I owe you (perhaps this message), kidding
_________________
First lesson - English, not english. I, not i. ~A student of English

[Mister Micawber]

.
Yes, IOU-- 'I owe you'. It is usually a small personal note acknowledging indebtedness.
.
_________________
Native English teacher at Mister Micawber's