Would a canard work better for emergency pitch down?
A couple of confusion here. For starters, unless we are dealing with T-Tails, there is no deep stall for a tailed airplane. On the other hand, a canard airplane has the potential to enter deep stall.

Next, for a transport category aircraft, tail stalling in the positive incidence is generally not a concern. Tail stalling in the down load, however, is; for example, zero-G pushover in icing condition is a real issue to consider during design. In a well designed aircraft, the tail would have a higher sweep and lower aspect ratio than the wing so that the wing stalls earlier than the tail.

(Zero-G pushover may stall the tail because of the pitch rate build-up. Nose-down pitch rate equals negative flow incidence on the tail. Once the tail stalls, you lose the ability to pull.)

It could be an issue, however, if you have a T-Tail. For a swept wing in cruise configuration, the pitching moment would likely reverse near stall. At that point, the elevator would still have good effectiveness, but depending on how aggressive the pitch up is, there may not be enough time to lower the AOA before the aircraft enters deep stall.

Once in the deep stall, the authority on the tail as a whole decreases dramatically. Even with full nose-down stabilizer and nose-down elevator, you may not have enough authority to break the stall. In that situation, without an anti-stall chute, it's game over. The point is, you don't want to ever get there. Preventative measures include stick pusher and envelope protection functions.

Would installing a canard help? Sure, more authority always helps. But does it warrant the complexity and weight increase when other solutions exist? Probably not.