Hi! I use several Apple usb-keyboards on my Mac Pro. They work fine.
I can get "@" using "righ-option (righ-alt) + 2"
"(" and ")" using "shift+8" and "shift+9"
? using shift+'
and ! using shift+1
Check your Region and Language preferences on Solus System Settings because when installing if I chose my Spanish Macintosh keyboard after installing it may be selected but keyboard layout doesn't match Spanish (Macintosh) I just delete it and choose it again.