This is probably going to be tricky...
Edit the first boot entry "start Fedora...." by pressing e. And then navigate to the linuxefi line, and find at the end of that line rhgb quiet and delete both. Then F10 or control X to boot. You should get some idea of where it's failing.
I'm going to bet dollars to donuts that this is USB-C / USB 3.1 Gen 1 / Thunderbolt 3 / PCIe confusion. I'm having this problem on a USB-C only HP. What's going on is, the port is really a PCIe port until there's an adapter. And this instantiates correctly later in the boot process, but does not happen correctly if the adapter is already plugged in when the adapter is connected. But we have totally different hardware so you may have a totally different problem. But my guess is that's the issue so the long and short is this is probably going to be tedious.
Anyway, once you get to a dracut shell, it might be possible to connect a USB-C to Ethernet adapter, plug in a wired connection (I know seriously) and then do this:
And you'll get a url to write down somewhere. That URL hopefully will contain all the kernel messages for booting and figure out WTF is going on between the kernel and these ports.
There's been a metric asstonne (this is an SI unit) of PCIe changes and also Thunderbolt 3 stuff, in recent kernels so it might turn out we need to get you to try Fedora 26 Alpha candidate (yes I know seriously) to use a newer kernel that might have a relevant patch.
You've already resized the volume in Disk Utility first? Definitely do not let the Fedora installer resize/shrink. It'll cause total data loss on the macOS side. So you can do that in the meantime.