Look up "noise gain" in the literature (or internet) since it's a very important topic.
For gain 100 or 1000, there is very little difference between the closed-loop gain and the noise gain.
When measuring input offset voltage with such a gain configuration, using split +/-15 V supplies, you would normally connect the bottom end of the feedback network to the non-inverting input, and then connect that node to ground, unless you really need to measure the offset voltage at a certain common-mode voltage.
If you are using a single supply, then connect that node to an intermediate voltage (such as half the supply voltage) and measure the output voltage with respect to that node at the intermediate voltage.