Wide array of weird problems on new laptop: live installation, grub, shutdown

Hello. I have a couple of questions about a variety of issues I'm facing with my new laptop. I know this sort of scatter shot approach to a thread isn't particularly recommended, but I'm baffled by some of them, and I thought I'd share all of them in case readers have any insight into one or more of them. First up, the laptop: It's a MSI GS60 Ghost Pro-002. with a Core i7 (6700HQ 2.60 GHz) and an Nvidia Geforce GTX 970M, 128GB SSD and 1TB HD. Came installed with Windows 10 obviously, and for the sake of trying, I figured I would dual boot this machine instead of wiping Win10 off completely. So I got last nights build of the amd64 install of 16.04 and got it installed to a USB drive. Here's where the fun starts.

1) Live Installation: tl;dr: Couldn't get to live desktop no matter what I tried, but selecting "Install Ubuntu" straight from the boot menu worked.

For the life of me, I could not get it to work. I tried every combination of nomodeset, i915.preliminary_hw_support=1, pci=nomsi, nouveau.modeset=0, and anything else I could find on Google that seemed relevant. The pci setting actually prevented the wireless firmware from working, so that was out. The i915 and nouveau settings didn't make much difference. Nomodeset was the only really helpful setting, although it still didn't get me all the way in. It stopped the live environment from hanging while booting up, and got me to point where I could see the default 16.04 desktop background, but none of Unity would load in, and I could kind of see the "Unity ran into an unexpected problem" dialog pop up where it wants to send an error report. The problem was, any window that appeared would be flashing in two places, one in the upper left coer, and again somewhere near the middle of the bottom of the screen. Effectively unusable. After trying to solve this for nearly two hours, I gave up and simply chose to try to install Ubuntu (with nomodeset) and to my surprise, it worked perfectly (relatively speaking.) So I can install just fine, but if I need a live environment, I'm out of luck.

2) GRUB: tl:dr; After installation, no grub menu, boots to Windows. boot-repair utterly fails, but I ultimately fixed the boot order in BIOS settings.

After the install completed, the laptop rebooted, and went straight to Windows, no GRUB menu appeared. When I was doing the installation, I chose custom settings, because I wanted / mounted on a SSD partition, but I wanted /home mounted on a new partition on the HD. It asked where I wanted the boot installation, and I chose the SSD device, but not a specific partition (wasn't sure what the best option was tbh). So I was able to pull up the boot menu by holding F11 at the MSI logo before Win10 launches, and choose the ubuntu partition, and launch GRUB. I figured the smart thing to do would be to install and run boot-repair. However, it would always get up to the step that says "Unhide boot menu. This may take several minutes" and effectively hang. Progress bar stopped, and I couldn't even open the System Monitor to see what the CPU was up to. In the end, I fixed it by going into the BIOS and promoting the Ubuntu partition above the Windows partition, and although this fixed it, it feels like I cheated or something... That doesn't seem like the right fix to me, or am I being stupid?

3) Shutdown: tl;dr; Ubuntu refuses to shutdown. Constantly see a tail of NMI watchdog reports about CPU #0 or #2 being stalled for 22/23 seconds.

That's actually all there is too this one, not much else to report. Kind of troubling, I Googled a bit on this one and couldn't find much. I end up holding the power button down to force it off. Less than ideal.

Does anyone have any thoughts about all of this? Things I should have tried, or should try if I factory reset the machine and try again? (which I'm sorely tempted to do.) I wasn't sure about my partitioning strategy, especially since Win10's is so complicated to begin with. But I basically carved out about 24 Gigs of the SSD for the root installation, and about a third of the HD for the ext4 /home mount partition (and another 4GB for swap). Would love to know what people think. Thanks very much for reading this and for any help you can provide.