I need help transcribing the word in the red box: has anybody ever encountered this abbreviation/spelling before? Could anybody point me towards a resource that answers my question? I've looked in Cappelli, but nothing so far.
It should say Inas or Ina. Ina, whose name is referred to as Ine on Wikipedia (unclear if this is because of a modernisation of his weakly declined Old English name or because ancient sources are also inconsistent), was the only king of Wessex who had a father named Kerend (Wikipedia spells it Cenred). Wikipedia also Latinises his name as Inus although the name of his law book was Codex Inae, implying his name was first declension. I can't tell you why the letters are the way they are though -- this is not a standardised ligature.
I found this by googling the snippet "dei gratia westsaxonum rex exhortatione", which led me to a Google Books scan of what, confusingly, appears to be multiple books in a row, but this is the crucial part.
This book from the 1600s transcribes it as Inas.