The update should have given you the dedicated media slider as an additional option. When adjusting volume, there will be bell on the left. Tap once for vibrate only, twice to go into additional interruption settings.
On the right, the three lines button gives you the various volume sliders.
For auto brightness, I downloaded an app called slider widget. It has multiple volume sliders as well. May help with above too.
W.r.t. 16Gb.. Get a bigger sd card. The update handles transfer of media ( and since the last update, apps too) to the sd card rather smoothly.