the stuff between the commas

[LFG List]

Dear LFG Friends,

I have run into problems analyzing the stuff between
the commas.  Call it apposition, or call it whatever,
but once again, I am stumped.  Without going into
great detail, how might we figure out the C-structure
and, more importantly, the F-structure?  Do you know
if sentences such as these are analyzed in any LFG
text books?  Anyhow, here they come:

1.  The airplane, I believe, arrived.
2.  By God, and God is almighty, you bought the car!
3.  We, the undersigned, protest.
4.  At the show are cars, if you are interested, imports.
5.  The friend is Peter, may God bless him.

I eagerly await your opinions and suggestions.
Thanks in advance from Abu Sammy.