I’m not familiar with the “blinker problem”, but your copying around of pip was probably ill-advised. For one, you didn’t copy the correct “pip” into the venv. Also, there’s more than just pip in the venv bin directory to consider.
If you’re not too far down the road with the install, I’d advise starting over and using the tactic of setting the environment variable that’s discussed above, which would be this:
export DEB_PYTHON_INSTALL_LAYOUT='deb'
curl -s https://mailinabox.email/setup.sh | sudo -E bash