Sorry you're frazzled by your Inspiration. I hope someone chips in with the settings that work for them. I would like to chime in with a few suggestions of my own
First, I do want to make sure you've ran the updates here: Inspiration - Pazzles
Second, I'd like you to read this blog post: Pazzles Craft Room • View topic - Trick for Determining Blade Length and Pressure
. It's probably the best description for determining the correct blade length. You want the blade just deep enough to cut. Any deeper and it will score your mat, and the blade won't turn in the housing, and that's what tears paper. Sounds weird, but shallow blade is better a lot of the time.
Third and finally is finding the right pressure. I've not used SU!, but I've heard it's a bit heavier and can have a different weight from color to color, which of course makes it trickier. The pressure settings on the Inspiration are so powerful, we recommend you only change the pressure upward in increments of two. Yep! Two! So, for your SU! cardstock, you might find a blade length of 2 will cut through one layer on the 'fold test' described in that blog post. So, start at blade 2, pressure 18, and cut a small circle. Didn't work? Try blade 2 and pressure 20. Keep cutting circles until one pops out clean. You'll find the magic spot!
Other things of note: try cutting slower. I prefer to cut a little slower when I am working with something more 'sensitive' or intricate, and I will only cut fast when I'm cutting something super-simple, like a plain box.
Also, humidity can be a big big big factor. If you live in a humid area, your paper will soak some of that up. We tell folks in humid areas that blade length and pressure go down, not up! At Pazzles Corporate, we are in a very dry area with almost no humidity, so if you're somewhere humid, take everything we say and turn it down a notch. Make sense?
I hope this helps. Since you are still under warranty you are totally welcome to call tech support and we'll get you going over the phone or on chat.