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I just found your post. I'm not sure where you should go next; but great job getting this far! Never give up.
If you require even better stability you could punt back to Debian 8.8 (via live and installer for KDE if you want) for a month or so. Especially if you have stable work to do.
A lot of good and respected work has been done to test Deb 9 into it's "stable" rendition; but is brand new and just now hitting the masses.
When Deb stable is just a few days old then it is stable on the devs computers. The masses bugs then make it better for all the many multiples (exponentially) of hardware combinations and personal UI preferences. Therefore for mission critical applications it's best to wait a month or two and that takes self-control.
Plus, things are getting more complex and numerous, not less.
Plus, a major dist release means core/foundational improvements (never stuck in the past) and these also require more vetting.
All that said: You'll never find better than Debian. If you *construct it from your GOOD choices.
If there are any brand new GNU/Linux users seeing this then start with Linux Mint Mate (EASY) for about a year. Then install Debian (hard the FIRST time) and make it the exact *way you want it.