Gnome Tweaks, installed with Ubuntu Software, should work. I also have the two settings (changed in dconf interface) you list (same values). Additionally, the org.gnome.desktop.draw-background is set to true.
I remember having problems with this in Gnome Classic on 17.04 release. It worked for me eventually, might require session logout. Try using dconf instead of gsettings.
If you have gone through many consecutive upgrades between Ubuntu versions a hard reset might be necessary first. This command will reset all your desktop settings in 17.10 to default so use as a last resort (I had to do this myself for other reasosn): dconf reset -f /