For the missing x64 WinPE image, see this article:
You have to enable the x64 detection. From the article:
• x64-based client computers do not receive an x64 Windows PE boot image. This can occur if the PXE basic input/output system (BIOS) implementation of the network booting computer does not correctly identify itself as being capable of working with x64-based computers. To work around this issue, enable architecture detection in the boot programs. To do this, run this command on your WDS server:
This was exactly what I needed to do to resolve my problem, thanks!