Cool, didn't noticed you changed it to your actual partition, although I should have because there's no reason for me to have 4 partitions on my disk. That being said using UUIDs for booting is better than device names, if you add or remove a drive the device name can change. In my case it's a laptop and only has one name slot so I'm fairly sure it won't change, plus I had to write that file manually when I first installed my system so I was lazy and used the device name, but you already seemed to have the proper UUID there, so changing it to the device seems a bit backwards.

GRUB is also customisable, although I agree that refind looks a lot nicer. I don't think refind is any better than GRUB in dealing with Windows updates, the problem is that Windows has this annoying habit of formatting the MBR so it essentially wipes all other boot managers from the drive, which is why people recommend having windows in a different drive so it can't fuck up your boot manager, but I know that's not always a possibility.

As for the splash screen being wrong I can't help you there, I actually like the checks scroll that's the default without a splash screen so I've been using that for a while now.