Q1) I assume you mean that the chapter points you have set are sitting on solid black frames? Piece of cake. Select the chapter marker in question, move the timeline marker to a piece of the clip that is not black, presumably about 3-4 seconds down the timeline, and right-click on the time indicator OR the chapter marker, and choose "Set Poster Frame"...
Q2) If your footage was already in DVD format and you added something in front of it (i.e. any content layer from a Photoshop file which is anything that doesn't have a name in paretheses (+), (%), (=1), (=2), (=3)) forces the need to re-render the motion menus. In short, if you put ANYTHING in front of a motion menu, Encore will need to re-render the whole thing.
Q3) If a menu doesn't move, you do not need to set a duration. This is a minor bug... Encore should grey out this option under these circumstances.
Daniel Brown, Sr. Evangelist, DV & Motion Graphics
Adobe Systems Inc. -
http://www.adobeevangelists.com