The Edge driver “Zwave Switch” includes support for dimmers too. There’s no separate dimmer driver.
As to why they aren’t returning to their previous value, I do know that different dimmers treat zwave commands differently. Some interpret an “on” to always mean “on to 100%” vs “on to whatever the last value was”. It sounds like the stock drivers are either not handling those differences for your devices or they just force do it one way or the other.
For your GE models, you can try Phil’s GE switch/dimmer community Edge driver, available here. See if that helps or makes a difference.