How long does it typically take to see the whole musuem

It all depends how long you take to read various parts. Flow of traffic is about 2 hours but you could easily take longer.

At least 2 hours

I arrived at 12 noon and left at 4 with 45 min for lunch

1 hour or more

I would dedicate about 45 minutes to see both memorials if you know someone who died there and are looking for their names to place short roses on.