Do you clench your fist hard?
No, the fist is tensed only on impact and not very hard, you are not squeezing anything, you tense it only enough to make a closed fist.
You should experience no tiredness or fatigue from closing the fist, if you do you are tensing to hard.

You turn the fist over?
Yes
Four basic punches, jab, cross(straight right), left and right hook, should all finish with the palm facing the ground.

You do not contact/tense your shoulder/chest on impact of a punch

You contract your fist on impact, punches should go through the target to successfully transfer the weight/power.
You hit much harder punching through the target.

Also how long do you tense the fist for and how long do you continue to keep trying to drive through the target??

The fist is contracted for a very short time thousands of a second.
You drive through the target because it is more powerful, hitting the heavy bag, pads or opponent will give resistance, so you might not be able to to fully extend the arm, but this should be your objective, standing to close to a heavy bag you will be unable to fully extend your punch.


(ive got the hips and legs doing the right thing im not off balance, im transferring all my weight it feels very heavy, my punches are very fast, im pulling my punches with my midsection and shoulders im not pushing them, im getting snap from the shoulders, im just not sure what is to be done with the chest shoulders arms and hands apon impact.

Delivering a punch is like kicking a ball, all your muscles are involved, but you do not need to over think which muscles need to contract,(calf, hamstring, quadriceps, gluteus maximus, hip-flexors, abdominals, trapezium, latissimus dorsi ) or be in such a position because you are preforming a technique.
If kicking a ball, tensing the muscles would be counter-productive

Punching is a complex technique and moving your limbs will contact and relax hundreds of muscle fibers.

Do not tense any muscles, they will do this on their own accord.
Eventually like walking you will just walk instead of thinking about how to walk.