Use the search function brosef. We already discussed this in a couple ongoing threads. BOTH of the threads have the word "trap" or "trapper" in the title. And just in case.... YES THEY DO! ALL OF THEM! They also benefit from "+pet dmg" items, which is the kicker in making a good trapper. They DO NOT benefit from "+pet armor/speed/health" or from "increases elemental/lightning/fire dmg" items, or from any stats such as strength/dex/magic, or from "critical hit chance/%dmg" increases.
This build is a fun one! Good luck. I'm been at level 100, down to lvl60 of the SV, and I'm still not bored of it yet. Get some blood skellies too.
I've never heard of pet mastery buffing your traps, but it sounds possible, since the hover text does read "**** seconds summon duration" on your traps.
I don't think pet mastery does anything for Devouring Trap, though. I have level 1 DT and i have level 10 pet mastery; they don't affect each other.