Walsall went close early on when Clayton McDonald's header from a corner was saved by Alan Julian.
Jackson then sliced wide after being sent through by Howe before firing a further two first-half efforts straight at Walsall keeper Clayton Ince.
Gills continued to spurn chances as Jack Payne failed to convert Howe's low cross from the right and winger Andy Barcham fired over.
Howe saw a close-range shot deflected wide after 55 minutes and only a McDonald tackle prevented Jackson converting a Barcham through-ball 10 minutes later. Jamie Vincent blocked Mark Bentley's shot on the goalline with five minutes to go to deny Gillingham victory.