1. Yes, as long as you have Audiogate or another appropriate dsd playback/editing software...With Audiogate(if I'm not mistaken) it's not true dsd playback, it will convert on the fly to whatever the settings are set to, 24bit/192khz is the best it gets, it sounds really good to my ears.
2. I started out using WSD but the file size was a bit ridiculous for what I'm recording(small local bands) and have since been using DFF.
3. I have never used the output filter myself, but others may have a varying opinion on that.