You don't need IP to get the correct soft proofwiew in PS as a comparisment to those prints you got from your "IP" test.
So unless you had paperwhite checked when soft proofing there is nothing wrong in what you did when trying this(as I see it)
I only check the paper white to check "overall" color changes that the paper will produce.
But mostly leave it unchecked when doing my adjustments.
I know some of the "big" guys out there recomend checking this during the whole soft proofing
I've found that only usable if your "print wiewing setup" is sitting right next to your display.
In my case it's located 90 degrees to my left,so unchecking it gives me a a more "correct" wiew when it comes to blacks and contrast etc since I find the blacks look kinda washed out when checking this compared to the print.
I still do think that a little bit in this problem might be the epson profile.
I do think they tell a bit of a lie between soft proof and print when it comes to deep blacks
However I kinda have the feeling that this(if you tried it) would probably not change anything for you as a closer match between soft proof and print.
And since I know nothing(only what I can read on the net) of the software you're using when calibrating you display, and I'm located in Sweden and you're located in Canada.
It's not like I can swing by your place to see for myself what you see
I'm actually starting to think (as you say yourself about those deep blacks) that unless your calibration is a"little bit off"
they tell little white lies about deep black situations.
when soft proofing.
If this would be the case.
How about creating a adjustmentlayer that corrects for those dark shades as a visuall guidance while softproofing to make sooft profing a bit easier.
And just deactivate it when printing.
But then again there is always the chance to forgett unchecking it and getting a spoiled print =)
Anyway.it's been fun/frustrating/intresting trying to figure out the cause to your "problem"