keyboard questions.

I hope someone has a few minutes to address some keyboard
questions.  I'm pretty dumb about keyboads.

I am running on a pretty much standard Debian Linux (Knoppix).
I want to run 5250 sessions in the same X session with browser
mail open office console sessions, in otherwords everything.
So:
1.  My understanding is that if I leave .Xdefaults alone the other
       apps will be unaffected by, for instance, my mapping
        Enter to Field Exit.   If I do that mapping in /usr/share/tn5250/XTerm,
        it will take care of the 5250 sessions and not affect anything else.  ??
2.  My (barely) understanding is that  the default(?)  file
      ...../i386/qwerty/us.kmap.gz
      maps  scancodes to 'names'  like   Escape or KP_ADD.
      then a filter file like XTerm can use those 'names'  to map to ascii
      sequences.  ??
      If that is correct, what does the mapping in lieu of XTerm?
       and what happens to all the keys which XTerm doesn't map?
       Is XTerm an override of a broader mapping?  Pardon my ignorance.
3.  The next step in the process would be what is sent to the AS400.
       As far as data, should I just assume that if the proper CodePage is
       selected, the correct ascii/ebcdic  and  ebcdic/ascii translation will
occur?
       I am aware for instance there are subtle differences between
       Spanish(Spain)  and Spanish Speaking(Mexico).  Not that that particular
       one affects me.
4. Back to scancodes.
           There are keys which need to act differently.  Like Right control
   and Left control.  If I use us5250.map (which looks like a more thorough
   mapping than us.kmap.gz.  Would I do a loadkeys?
   Then if I map Right Control to  5250 Enter (which is what my users are used
   to)
   would other apps  lose that a ctrl key?  Again pardon my ignorance.

   Thanks.