require-dev is not the place to develop dependencies. It is meant for software that is used only in development, like PHPUnit, Mockery etc., or for dependencies that are useful by themselves, but in this case only used for development, like the client library for the service a software package is about (to make some real requests in a test scenario).
So your library shouldn't have been "require-dev" from the beginning.
Another thing is: Composer will deduct the version if use appropriate branches and tags, i.e. a branch named "1.0.x" in your repository will be detected as being the development branch for all 1.0 versions, and any requirements for such versions could possibly be satisfied by this branch - provided you allow for development versions either by setting
"minimum-stability": "dev" (which would allow development versions for ALL software - rather unintended), or when you require version
"1.0.0@dev" for your software.
The one thing that might currently break your composer setup is that you mention a version in the librarys composer.json explicitly, and this is a development version. Have you removed that version indicator? You should remove it, because life is easier if Composer can detect the versions from the tags in a repository, not by having them explicitly mentioned in composer.json.
Finally please make sure that when using Git you tag the commit with appropriate version. The
required version should correspond to the git tagged version.