Penny,
1) The only easy way to do this is to create a custom layout (see
http://www.adobe.com/go/learn_lc_fgCustomizing). You could copy a One Column layout and then change the VBox that wraps the PanelItem to a HBox. This way you can layout items horizontally until a Next Area item is encountered.
2) The beauty about Form Guides is that you don't (usually) have to do anything special to edit values / presences in the Form Guide - they are driven off the value / presence in the underlying PDF.
In your radio button, you could do something in the calculate event like "if (this.rawValue == 1 && this.resolveNode("someOtherField").rawValue == "somethingElse") { this.rawValue = "2"; }". This will force the value of the radio button to 2 in both the PDF and the Form Guide (based on your business logic).
John.