I've found that connecting my PC directly to the router with a LAN cable solves the download issue. I can now complete the download and get to the installing phase every time.
Unfortunately, it now fails to finish installing after the reboot and has given me a few blue screens. I can't say I'm surprised, I fully expected that to be the case.
Still, if anyone has yet to try a wired connection, it solved at least this particular issue for me. I don't know why, my WiFi connection tested well with no lost packets or other issues, and I've had no trouble downloading other large files or drivers.