Disappointing to hear about those issues. I haven't experienced them with my XPS 13 (1080p, i5-6200U), but your experience certainly makes me wary about buying another down the road.
I accidentally got the top-end model when trying to make sure I got 16GB of RAM and a 512GB SSD, so i7-7500U and the high-res touchscreen (neither feature of which I want), but I got a great deal regardless as they were putting out the 7-series revision.
I love it, and the only issue I've had was a combined update reboot with a Dell update and a Windows 10 update. The UEFI 'lost' the SSD, which took some Googling to fix.
I'm also honestly surprised that you've had persistent issues with Dell's service. I don't blame you for looking elsewhere in light of your experience, but I'd hope that that isn't the norm these days!
[you might try escalating your issue, if you care to- this might result in Dell going out of their way to address the issues]