It's very easy to walk between terminals 1, 2 and 3. In fact it's a good way to stretch the legs between flights. If you walk slowly and look in shops one lap can take about an hour (much less if you are walking purposefully). There are also driverless trains that cover all combinations of terminals including an impressive line that takes you past the rain vortex. (I think it's the T3B <> T2E line.) It's well worth seeking out.

In your position I'd grab a 6 hours room at the Ambassador than walk / ride / eat / drink the rest.