The power pad should connect to ground for best thermal conductivity, although if it wasn't, it wouldn't affect communication.
AMC7812EVM and samples can be ordered through the following websites:
http://www.ti.com/product/amc7812
http://www.ti.com/tool/amc7812evm-pdk
On a different note, a colleague of mine looked over the schematic and found a few possible mistakes. Currently, Q14 and Q19 of the schematic show to have a floating base and, as a result, will not work for remote measurement. To correct, both transistors should have a short connection from base to collector. An example of this connection is found in the EVM schematic attached to an above post.
I’ll also be out of office next week for the holidays, and will be back during the first week of the New Year. Thank you for the Holiday wishes and have a Merry Christmas and a happy New Year.
Matt