What do you mean, it is connected to the 5V and GND...
Your diagram clearly shows the excitation points of the bridge connected to the input of the amplifier, the excitation of a bridge should be connected to the supply voltage
I haven't checked that but if i remember correctly it was somewhere in the 2.5V range...
Being 'somewhere' in the 2.5V range, with a bridge is not accurate enough.
What do you mean with nulling L/C offset in one sense only?
As the 'variable resistance is connected to only one input of the IA, means its only across one arm of the bridge. which means you can only reduce the effective resistance of that bridge arm.
The IA output is always 2.90V - 3.10V now no matter if the load cell is pluged in and stressed or not.
The output of the IA, with Vref connected to 0V, if the bridge is correctly balanced, without any load, should be close to zero volts.
the Load cell i'm using has 120ohm bridge, so i need to use 10ohm gain on IA to get decent values.
The value of the bridge arms [elements] has no effect upon the gain setting.