Dear Michelle,
As Predrag already pointed out, if your dad belongs to I2-PH908 and has similarity to his results, there is a very high chance that he belongs to a more specific branch FT16449. We already have number of of those who did Big Y test through myFTDNA or similar test by Dante Labs, and these tests can better point where your father's family fits on I2 tree and with whom he might share ancestry at some point in past.