I've just seen this thread, and I find it fascinating. I wish I had all the answers, but I fear I don't have many at all.
I can say what the vase isn't. It isn't Carnival Glass, by strict definition. There are several "crackle" effect Carnival patterns (Soda Gold, Crackle, Tree of Life etc) but they are moulded patterns that give a crackle effect. They are not a treatment or part of the glass process.
The iridescence is applied, as all iridescence is. Usually it is applied when the glass is hot - very hot. But it can be applied to glass that has been made some time ago. The lustre is applied to the cold glass and then the item is fired in a kiln. It's a tricky process and needs very skilled hands (it also results in much breakage) but it can be - and has been - done. Terry Crider and the Hansen brothers were experts in the field.
I don't know if yours was done in this way, I'm just pointing out that it's possible.
The rose pattern is fascinating. When I first glanced at it, I was struck by a resemblance to Brockwitz Rose Garden pattern.http://www.geocities.com/carni_glass_uk_2000/RoseGarden1.jpg
Of course that could be because it is my favourite design! But it did remind me a little of it.
Anyhow, I haven't answered any of your questions really, all I can say is that it isn't true Carnival - but is is fascinating and lovely. I was wondering if a "local" expert in iridised studio glass may help you. Try contacting John Cook Studios in Oregon. They make some gorgeous (oh so gorgeous) iridised glass. Here's their website.http://www.johncookstudios.com/index.html