switching DAC output to multiple inputs
If understand correctly you are looking for a simple multiplexer, something like the 74HC4067 should do - it's a 1 to 16 multiplexer/demultiplexer.  





Simply input your signal to pin 1 (COM IN/OUT) and use S0 to S3 to switch it between I0 to I15 (each of which are connected to your Arduino inputs) 
For example if you want to connect to I7, then you set S3 to 0, S2 to 1, S1 to 1, S0 to 1 (i.e. 0111 binary = 7 decimal)  

This is a single supply IC, so it won't work if you DAC swings below ground, in that case you will need a dual rail mux (plenty out there, e.g. 4051 is an 8ch dual rail)