First, to clarify, are you setting up the dual-boot with Solus and Windows or had you done that before (and now the system won't boot to Solus)? Can you give us a little more detail about the problem you're currently having?
"mount: /mnt/solus/boot: mount point does not exist.
That's probably the problem there. Try doing creating that directory before trying to mount it:
sudo mkdir -p /mnt/solus/boot
sudo mount /dev/sda6 /mnt/solus/boot