For small groups and overdubs, the easiest way to do headphone mixes is with the cue sends on the ssl

Patch the stereo cue out to mymix input 1-2, then cue 1 left to mymix input 3, cue 2 left to mymix 4, echo send 3 to mymix 5, and echo send 4 to mymix 6. Do it exactly like this and it will work properly with talkback going to the stereo cue and cues 1 and 2, but not 3 and 4. 

If you’d like click to be on its own send, which I’d recommend in most cases, pick an unused output of pro tools, I often use output 48, and patch it from one of the green row outs 48 into mymix input 16

You could also choose to patch the “MD” (music director) output into mymix 15 and use that as a separate dedicated talkback channel by using the MD button or the MD remote switch