1) After you edit the quality presets (Modify, name, save), you must apply that modified preset to your asset. It is a two step process. You describe only one "ok," so I think you have not applied the preset to the asset.
You select the preset (including your modified one) in the "Transcode Settings" panel, not the "Edit Quality Presets" Panel.
That should help you get the quality you are looking for.
Note that slideshow quality is determined by the default transcode for the project when set to bluray.