Welcome, Matt, to OEM.

I’m afraid I can’t help with the emonPi, but one of my colleagues should be able to help you. Unfortunately, you’ll have to wait because they’ve probably gone to bed. (It’s 00:45 local time here in the UK as I write.)

When it comes to your 3-phase installation, bear in mind that all the emon kit is designed with the UK domestic power system in mind, so the sketch in your emonTx will need replacing by the 3-phase one (posted here: Update to 3-Phase PLL sketch - #15 by Robert.Wall) unless all your loads are balanced.