AD625 instrumentation amplifier simulation model
There is a SPICE model for AD624, but not for AD625. The two amplifiers are very similar, importantly the same GBW and Vos, but not identical, as the 624 incorporates a few extra resistors on the input to simplify gain control. 

Open the two datasheets side by side. You may be able to modify your 625 circuit to incorporate the 624 resistors. If you can identify those input resistors in the SPICE file, you should be able to delete them from the model, and bring out the internal nodes.