There is nothing Howard can do short of miraculously finding a new Jackie or Artie, which will probably never happen because both of them were freak accidents of luck in his life.
He is completely talentless. Listen to a show before Jackie joined or a show after Artie left. It is unlistenable shit, despite the presence of the great talents Robin and Fred. Howard's entire career consisted of a) Jackie making him seem funny and b) Artie building on that momentum and carrying the show for a few more years.