Please try not to full quote everything. The threads get very annoying to follow when they are mostly filled with just blocks of quotes.
You can reset the "Clipped samples in track" field name to the new default string by right clicking the option name in advanced preferences and select 'Reset':
Note that these changes only affect what the tag fields are called. Files that are already scanned will stay the same. You could use foobar's Properties dialog and its 'Automatically fill values...' feature to copy data from the old field to the new one. Or you could rescan the tracks if there aren't that many.
Another option would be to use titleformat code with fallbacks and support showing data from multiple field names.
As for how to show the data, most field names you can see in the preferences window. For example to show data for the clipped samples, copy the field name and add percentage signs to both sides of the field name, like this:
%truepeak_scanner_clipped_samples_track%
To support also the old name, you can use this:
$if2(%truepeak_scanner_clipped_samples_track%,%truepeak_scanner_clipped_samples%)
Note that foobar2000 displays a question mark by default for a missing field, to hide that use square brackets around the part that will be hidden if metadata isn't present:
[%truepeak_scanner_clipped_samples_track%]
or for the longer one:
[$if2(%truepeak_scanner_clipped_samples_track%,%truepeak_scanner_clipped_samples%)]
The Loudness Range (LRA) gets stored in tag fields that are already used by some tools. The fields are called replaygain_track_range and replaygain_album_range.
Note that capitalization doesn't matter, foobar2000's properties dialog shows them with all caps by default.
To show LRA value for a track, you probably want to use something like this:
[$replace($if3(%replaygain_track_range%,%lra_track%,%lra%), LU,, dB,,)]
The square brackets means it won't show a question mark if the info isn't present. $replace() part removes ' LU' and ' dB' from the end. And $if3() part picks data from any of the given field names, first from quite established %replaygain_track_range%, then it checks %lra_track% and last it checks just %lra%.