Well I got it working last night!
It turns out that Windows was the complete failure here. Windows 7 has a bug where if you have 2 networks the firewall settings apply ONLY to the FIRST to connect. The second gets the default config and there is no option to specify interface. The only way to make it work was "Run, service.msc, find Windows Firewall, Stop & Disable".
I knew it couldn't be this hard...
Apparently the slave ID on Modbus TCP is ignored as the IP inherently only points to one device, only RTU checks the ID.
Also the R/W mix I have not tried, I put a standard read inputs FB and it did not work until I figured out the firewall thing. Just for fun when I have more time I will see if R/W mix only works for Unitronics stuff.
Thanks for the help, even though it was Windows all along....!