If my father is uncircumcised, should I retract the foreskin when bathing him?
Sounds like you are doing everything right. You are correct that when cleansing someone who is uncircumsized, you should retract the foreskin. Do this gently, and carefully wash the area. Then, be sure the place the foreskin back over the penis when you are done.
As for cleansing the backside, it is better to wipe from between the legs up towards the spine to be sure you clean out everything in that area.