Hello Steven,
I think you have a couple of issues outstanding here, from your error logs I can see two things.
1) Git does now seem to be recognized in your PATH, however it is getting error reponses returning that the addRemoteGit command failed.
2) The current version of Adapt Command Line tools does not use the repository "git://github.com/SpongeUK/download.git", the master branch has used a different repository since v0.017.
Is it possible that you are using an old or cached version of adapt-cli? The command :-
npm ls adapt-cli -g
will check the global version of adapt-cli that you have installed. The current released version is v0.0.21.
If necessary, you can update from an older version using the command :-
npm cache clean
npm update adapt-cli -g
Let us know what that comes back with and if you manage to get the CLI installed.
Chris