Manic Mary
Extra letters are
10 Across Small island as in Chiswick ???, so I is a misprint
20 Across Abbr for crown is CR, not ch
25 Across Def could be strip of Sn. Entry is U + NINETEEN reversed without the vowels, so misprint is 2nd N
32 Across is T with SEE + O +MALE reversed, so to fit the somewhat dodgy IMHO definition, the 1st E should be an N
35 Across Location of the oldest University in Germany. Capernoity is scots word for HEAD (HEID) + ELI(old priest) + ERG(bit of work)
2Dn Def = brand. Ring as in bells reversed with B in it gives the entry so last letter is a misprint
9 Dn is very tricky Def = causing paroxysms. anagram of SALT replaces E (250) in CONVENT. T is a misprint (end letter of 19Ac DOTIEST)
11Dn Crunchy stalks (think salad) Non fleshy = DRY
16 Dn Def = Exhausting. Swoop = DIVE including even letters of rEsPoNdEnT, so N is a misprint
18 Is a source of fossil fuel (think fracking). Robust = HALE + topped by anag of LOST, so T is a misprint
24Dn The Film is GIGI and ONE is ME. So the last letter is a misprint.
29 Dn 4 letter word for mixed school, which is an abbreviation of a much longer word. The entry is hdden in seCONDary. So the N is a misprint.