Hi Lionell,
No worries on keeping commenting. It always help because, it can be give a better understanding of the problem.
I found an ADC that is differential that is supplied from 2.5V to 5.5V. The AD7687 one of the candidates I found. The reference pin is external and can be connected with the power supply. The reference input voltage range from 0.5V to VDD+0.3. There is a circuit note for the AD7687 that you might want to check CN0225, http://www.analog.com/en/circuits-from-the-lab/CN0225/vc.html, Analog Front signal conditioner for industrial process control.
From what I understand, the stimulus or analog voltage measured on strain gauge are not dynamic. Usually for application that are not dynamic input voltage,sigma-delta ADCs are recommended.
I would recommend, you may check Sigma Delta ADC I found which is a single chip solution for strain gauge application. To mention are the AD7793 ( has on chip reference), AD7798/99 and AD7190.
Regards,
Jonathan