On point
#6 , you won't find a matte screen on a touch device, it simply doesn't work well.
From your list of specs, you may be best served looking at an iPad Pro 9.7" with the Apple Pencil. Yes, it's an expensive setup (and you said you don't want iOS) but for those uses and long-term viability it's probably the best solution. Samsung has historically left the tablets behind as far as even security patches, that's not even to mention major OS updates.
I have the 2014 Galaxy Note 10.1, it's really starting to show its age at this point. It's become sluggish to the point that some screen taps take several seconds to register and any app that has ads included is sluggish until the ads finish loading, sometimes registering touches on things I didn't want because the screen changed slightly.