Reading the history of the project on Multimedia / Kwave · GitLab, it seems that the developer has been supporting it for over 20 years; I don’t think he reads this forum nor that just suggesting these things would be useful to him.
I suggest you to contact him (Thomas.Eschenbacher@gmx.de) and offer to help on your first two points: you could rewrite the README in Markdown and make a merge request, or send it to him; then you could offer to spend some time moving TODO items to new issues.
If you help with these two things, your last two point could just become new issues in the Gitlab repo and the developer could see them as actual feature requests.
Are you willing to complete these small tasks to actually help improve the program the way you want to?