Thanks to Edward P. Arabas and Ruth Bowers for sharing your knowledge,
the answers were quite simple, actually!

My inquiry: Has anyone experienced trying to change a single label size
(amongst a
cluster of labels) then having unselected labels change size also? Need
suggestions on adjusting these fonts-request suggestions please.Will
sum.

Ed suggested:
Your theme was probably auto-labeled using the "Find best label
placement"
option.  If you Auto-label using the theme's "text label placement
property", this issue goes away.  (I haven't tried to figure out why.)
Or
you could use the Auto-labeler on selected subsets of your allotment
features to create smaller "groups" of auto-labeled features (then the
size
changes would be limited somewhat).

While Ruth forwarded this suggestion:
The reason this is happening is because the labels are sharing a
symbol.  ESRI does this to increase drawing performance.  Just off the
top of my head, you can use the following script to give them all
individual symbols.  This will probably increase your drawing time,
possibly the size of your apr.  Run this script from either a menu
choice or button (or just as a script).  It will only modify selected
labels.

v = av.getActiveDoc
if (not(v.is(view))) then return nil end
gl = v.getGraphics
s = gl.getSelected
for each g in s
  aSym = g.getSymbol.clone
  g.setSymbol(aSym)
end

Thanks again.  Debbie Rodriguez