Use the base of your palm to do the bulk of the pushing, and use other parts of your hand to get at the sensitive spots.
If you can, take a shower to wash off the massage oil after your massage.
Yes, you can do that if it makes you more comfortable.
You should know this and take everything I say with that grain of salt.
Listen and adjust your massage accordingly.
The P-spot can be found 2-4 inches inside the anal canal, on the front or anterior wall of the pelvis.