Assuming you are plugging the heater into the inkbird and plugging the inkbird into a 120v circuit you will be fine. The adaptor you built is for the inkbird output right?
You are correct that the element will draw 1375W. Would be fine on a 15 amp circuit.
I have that Inkbird PID and use it...
Not much. I use one on my RIMS, and it is fine. Hard to beat for the price.
There is a thread on the Inkbird.
https://www.homebrewtalk.com/forum/threads/inkbird-ipb-16-pid-controller-inquiry.627648/
You'll need a 3/4" NPT x 1/2" tubing adapter which may be hard to find.
Alternatively, a 3/4" x 1/2" NPT bushing and a 1/2" adapter like this
http://www.bargainfittings.com/index.php?route=product/product&path=36_56&product_id=170
Then for the camlock you'll need a female npt adapter...