[emerge glibc-2.18-r1 failed]

What is the output from

zgrep -i compat_vdso /proc/config.gz

 

The eblits are under ${PORTDIR}/sys-libs/glibc/files/ to find out more info

[Pure UEFI + Luks + ZFS ?]

No. If your hardware has efi you can do without grub. You do still need an initramfs if you put root on luks, and for zfs kernel modules if root is on zfs. ZoL is not recommended to be built in-kernel. That is a complicated setup, so I highly recommend you read the docs and get your questions answered before you start. (yes, this warning is probably too late)

[[solved] chromium emerge error]

What does issue 3770 say? The error sounds kernel related. I would guess that issue 3770 will tell you that you need to enable certain option in the kernel, rebuild, and maybe reboot.

[Funtoo problem with Icedtea-bin can't download file]

Have you tried to update your tree? Do you have "mini-manifest" in your Features?