Apologies for the delayed response.
Potentiometer R1 and resistor R2 are used for gain error compensation and not for the actual gain for the DAC.
Due to the architecture of the DAC, you would have a positive output using a single amplifier by having a negative reference voltage. Using two amplifiers with configuration similar to what you have suggested above will work as well.
You may want to check out the app note AN-320A and see Figure 1b which transposes the DAC configuration to provide gain. I have not tried this configuration but in theory it should work. Note that the multiplying capability of the DAC will be lost when you use this configuration.
If you only want to add gain to your circuit, you may want to take a look at app note AN-137 which discusses adding gain for a similar DAC configuration.