OK, first off I assume that when you say 'Channel' you mean 'Patch' or 'Preset', right?  In which case ...

1. You can only do this either manually (i.e. go in and edit each preset).  You can copy an entire patch  - i.e clone it - but not just a group of settings (e.g. a standard wah and expression pedal assignment.
   
   
   
2. Not entirely sure how you cut and paste on the Mac version of HD Edit.  On the PC you simply hold down the CTRL key then drag the patch 'name' up or down the list to where you want it. 
   
   Hopefully a Mac user will come along and tell you how this is done but, if not, you can always save the patch you want (using 'File - Save As' in HD Edit) then double-click on the opatch where you want the clone to go and do 'File - Open' to import the saved patch to the new location.
   
   Finally, the simplest way is to do it on the HD itself:  a) choose the patch to be cloned;  b) Press the 'Save' button once; c)  Use the second parameter knob to choose where you want the patch cloned to; d)  press Save again to save the patch to the new location.
   
   
   
3. For direct to PA you should
   -  make sure that you are using 'Studio Direct' output mode. 
   -  Try and use full range speakers or similar to build your patches to keep them sounding similar. 
   -  Leave plenty of room on the volume knob to boost patches if needed when you get them to the PA.   
   -  minimise the number of patches and amp models that you use.  It just gets too complicated and too weird for your bandmates if there is constant change in your tone throughout your performance.
   -  search this site for more tips regarding direct to PA.
   
   
4. Make sure you click on Send - Selected in HD Edit regularly to save the latest changes to your HD.   Use HD Edit to take a full backup (bundle) of the unit after a major edit session to keep your patches intact. 
   
   Also, learn how to edit patches using the controls on the HD.  There is virtually nothing that cannot be done in HD Edit that cannot be done direct on the HD and it means you are in good shape to make quick changes when you are performing/rehearsing when needed.