The first three bugs you listed are related to source maps. I haven’t used Firefox in a long time but I have experienced the same behavior in Chrome and VS Code

The first three bugs you listed are related to source maps. I haven’t used Firefox in a long time but I have experienced the same behavior in Chrome and VS Code when debugging TypeScript. It turns out, there was a bug in the loader that was generating source maps. Perhaps your issue is tooling and not the browser?