Need help with my initial attempt at a headphone jack switcher
You have got the right switch terminal diagram but the wrong switch!
Here's a photograph of the correct switch. Note the pin spacing.


You would need to wire the L &amp; R terminals of the output socket to A0 &amp; B0 terminals of the switch.
Like wise with the L &amp; R terminals of the input sockets to A1 &amp; B1, A2 &amp; B2 and A3 &amp; B3 terminals of the switch.
The common  terminals of the four sockets are to be interconnected.