last two i got these wrong .
(1) A couple following a substitute signature (4,5)
(2.)A cathedral dignitary leads the way and Hanna Jot is in a muddle being speedy (4,8,5)
I think johnathen swift but notsure about the 1st word Dean?

Yes, the first word in No. 1 is 'Dean' and the answer to No. 2 is 'Mark Twain'.