Two strategies for this: for the superscript one, regexp, and for the simple one just a case-sensitive search and replace:
(?<!abbr>)([A])(tt<hi rend="[^"]+super+[^"]+">y\.?</hi>\.?)
<choice><abbr>$1$2</abbr><expan>$1ttorney</expan></choice>
Att.
<choice><abbr>Att.</abbr><expan>Attorney</expan></choice>