An interesting pair of questions. Your first question, "Does he make his save before he takes poison damage or after," is answered above and under
Afflictions in the PFSRD.
You make the save in an attempt to avoid the effects of the poison.
Regarding your second question, "Does he get to take his actions for the round first," I had to do some research. I must be missing something in the PFSRD, as it isn't clear. For years, I've done poison saves at the beginning of the round. However, the following blog entry from Paizo states otherwise:
http://paizo.com/paizo/blog/v5748dyo5lc12
"3. The character must make a saving throw against every poison affecting him on his turn, but may make the saving throw at any point during his turn. If a poisoned character delays his turn, he must immediately make these saving throws. They are not delayed."
Based on that, you can still have your actions for the turn, just do the save at the end. Honestly, I'll probably still play it with saves at the start of the turn (or whenever we remember