I dislike all the picky picayune details of plotting (not Mathematica's fault — seems a problem in whatever system). Especially Inset and PlotLegends.

Here's a code to give you some hints (plotsfNN generated with PlotLegends -> {Row[{"\[Alpha] = ", alpha}]}):

Show[
  Flatten[plotsfNN],
  Graphics[{Arrow[{{5.5,0.055},{5.6,0.36}}]}],
  Graphics[
  Inset[                   (* edits to plot: *)
   Show[First /@ plotsfNN, (*   remove legending *)
    AxesOrigin->{5,0},     (*   or use Frame instead of Axes *)
    PlotLabel->None,       (*   remove plot label *)
    PlotRange->{{5,6},{0,0.04}} (* select highlight *)
  ],
  Scaled[{5.5/7,0.75/1.7}], (* fiddle with placement *)
  {Center,Center},
  Scaled[0.4]]              (* fiddle with size *)
 ]]

1. Use Placed:

   PlotLegends -> 
    Placed[{StringJoin["\[Alpha] = ", ToString[alpha]]}, 
     Scaled[{.5, .5}]]
   

2. Write Quantity[30, "AngularDegrees"] instead of 30 Degree

3. Use Inset.