From speaking to the person who does development for our localization tools, it seems that support for the editor’s built in translation tools isn’t something that we’re focusing on. The localization dashboard itself is supported but the idea of editing the translations in the editor, instead of exporting/importing, is something that has fallen to the wayside and is likely to be dropped. This likely was broken in 4.14 due to some changes with how the keys are stored so the updates may not be clearing the keys like it did previously. Unfortunately, you’ll need to stick with using third party translation tools for the translation itself.
As for the .po files not being marked as changed, I don’t believe that file changes unless you export the data. I’m unsure on the others exactly.