They could be more clear here if we knew something about your system.
inxi -c0zv8
after you booted from your USB
lsblk -f
and/or
blkid
would also help
Next is to chroot -
how to do this will depend on whether your system is using BTRFS or ext4 as a file system and whether it is encrypted or not.
Generally:
you would chroot, use pacman (not pamac) to update the system,
pacman-mirrors -f
pacman -Syu
watch for the result
and, because of your kernel issues, (re)install a kernel
pacman -S linux612 (for example)
regenerate the initrd
mkinitcpio -P
and update the boot loader
update-grub
exit
to exit the chroot environment
and reboot
… this will not do anything re your AUR packages, but the base system should be o.k. then …
…
we need to see or know what you see or there can only be vague general recommendations like this