Q. 2) See question above: If he can only hear with a hearing aid can he still be a Baal Tokea?
A. Poskim maintain that he cannot comply as an electronic reproduction of the sound of the Shofar is not acceptable.
If he can still hear a bit by himself and uses also a hearing aid, most Poskim maintain that he is not Yotze, since at least he is listening to a mixture of sounds from two sources, one proper and one not, and is similar to listening to an echo.
Poskim recomend that is such a case they should avoid using the hearing aid at least during the blowing of the Shofar (Minchas Yitzchok 2: 113, quoting H”T’P Frank zt’l, Piskei Teshuvos 589: 3, and others).
Horav Shlomo Miller’s Shlit’a opinion is similar.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a