Need help improving Russian Dips

Today has been my second workout ever involving these. I passed all the other elements leading up to this dip variation but I just haven't figured out how this one is supposed to "feel". I feel I mainly don't understand the upper arm support. 

What part of the body should be resting on the bar?

How should my hands be positioned on the bar? 

etc....

Here are a few of my sets today. I would love any critiques to make my form better and help me understand this dip.

Two major problems I notice are

1. My scapula is elevated rather than depressed in the upper arm support.

2. I'm leaning to far back for the upper arm support.

My lack of understanding in the upper arm position is holding me back on this move. 

 

Also, is the width between parallel bars to large? Should the bars be closer together? (Refer to the front view video) (The width can be adjusted)

1. You are lowering down to "Upper arm support."

2. Your bicep and tricep should be resting on the bar.

3. Your hand placement is fine.

4. The parallel bars should be at least, shoulder width apart.

A couple of pointers.

In the upper arm support your shoulder should be at or slightly behind your elbows. The first reps in the first two videos look ok, but then you lose it and your shoulders fall in front of your elbows. Also try to depress more.

The width of the bars should be the distance from your elbow to the fingertips or slightly more. The wider the bars are the more strength is required to keep the elbows down and shoulders depressed.