Hi, ethik,
35ac is an obsolete word that can mean “treat” as a verb. The grid entry is the two letters that you get when pronouncing the answer.
35dn has been discussed earlier. You need a five letter word that can mean “on earth” (as opposed to “in heaven”), around the normal IVR for Luxembourg. The grid entry is the first letter of the answer, followed by a letter that sounds the next three letters, followed by a letter that sounds the final syllable.
By the way, if Waterloo died in December, the editors must have intervened in the clue for 34ac, as the “Deceased Python” didn’t die until 21 January 2020.