I actually had that same Spigen case and got a replacement case for the same reason! I went with another Spigen Case. This one is a different, more flexible material that won't crack and it wraps around the whole phone. The only thing I missed was the cutouts for the volume and power buttons but I've gotten used to this one now! I like the look of this one too.
Yes, the Diztronic will work with a screen protector. I have a glass screen protector on my 6P and the Diztronic works fine with it.
An alternative suggestion for a case would be the Spigen Rugged Armor. This is the one I use daily and it's basically the Diztronic with a bit more style on the back (the inlaid carbon fiber accents). This one also works perfectly fine with a screen protector.
Spigen Rugged Armor: http://www.amazon.com/gp/product/B016CBFBVI?psc=1&redirect=true&ref_=oh_aui_search_detailpage
This is the glass protector that I'm using: http://www.amazon.com/gp/product/B019O5MN4W?psc=1&redirect=true&ref_=oh_aui_search_detailpage
iVoler Tempered Glass Screen Protector
Orzly Type A to C 4-Pack Cables
Thats about it so far, I'm sure ill be buying more cases and maybe a car charger in the next couple weeks after my device gets in my hands.
Nexus 6P Case, Spigen [Rugged Armor] Resilient [Black] Rugged Armor Ultimate protection and rugged design with matte finish for Nexus 6P (2015) - Black (SGP11797) https://www.amazon.com/dp/B016CBFBVI/ref=cm_sw_r_other_awd_7zjTwbDVPF39D
Nexus 6P Case, Spigen [Rugged Armor] Resilient [Black] Rugged Armor Ultimate protection and rugged design with matte finish for Nexus 6P (2015) - Black (SGP11797) https://www.amazon.com/dp/B016CBFBVI/ref=cm_sw_r_other_awd_7zjTwbDVPF39D
Like your #1 pick, I have the Spigen Rugged Armor which is a matte finish TPU case. It was $13 when I bought it, fits and feels fantastic. The carbon-fiber-look inserts add a lot to the appearance, and look much better in person than the product photos. I see it's like $18 right now though... https://www.amazon.com/gp/aw/d/B016CBFBVI/ref=psdcmw_3081461011_t1_B015EHQM14