You have identified all of the options that I would have suggested.

1) Keep the pump the way it is which I don't recommend.
2) Go with a 2 speed 2 HP pump. PB is probably correct in that you need a 2 HP pump for 6 jets running through the filter.
3) Go with separate pumps. This allows you to customize for the application but will cost you a bit more.

Option 2 will probably save you the most money in both hardware costs and on going electrical usage. The low speed of a 2 HP 2 speed pump is about the same power as a 1/4 HP pump so your electrical usage will be fairly low. With only 9000 gallons, you don't need much HP for circulation. 3/4 HP is probably overkill as well.

In either case, you may want the flexibility of having a separate pump for the waterfall so you can run it at the same time as the low speed circulation or while running the spa. It really depends on how you plan on using it and how much money you want to spend.