1 - Wow that cartoon software works pretty well!
2 - I use Audacity for all the editing of the Lucretius Today Podcast and it works well
3 - I know people swear by OBS Studio and have played with it but not found reason to use it - we record the podcast in Skype and I just edit that file in Audacity.
4 - The visual annotation feature looks like it is perfect for the type of video you're talking about.