My crack at the Sharpe’s father riddle: My collection of all the hints and clues dispensed so far includes the fact that we’re not looking for an historical character or a fictional character as such. That suggests more of a role or type than a name. You’ve said he was most likely a rogue and that he may have been French. And the word we’re looking for has 8 letters. So, my wild guess is: Corsaire Taking you out (removing the ‘I’) and putting you in (adding ‘me’) yields the letters corsaure, which means nothing in itself but it’s an anagram of Oscurare – which was the name of a very obscure American racehorse. Oh, and there’s a French comic series (and a band too I believe) called Joyeux Corsaire – happy pirate.
Helena