comma before 'and' [conjunction]: held in his right hand and his arm

[skarface]

Thank you for choosing to read my post.

A. "The gun was firmly held in his right hand and his arm resting on the armrest."

B. "The gun was firmly held in his right hand, and his arm resting on the armrest."

Q1. Is "And his arm resting on the armrest" a subordinating clause of "The gun was firmly held in his right hand"? Do I not need a comma before "and" or not?

Q2. What does a clause without a form of be, like "is" or "was", called?
Example: "His arm resting on the armrest."

 

[panjandrum]

To make this into a "good" sentence, omit the conjunction.
The gun was firmly held in his right hand, his arm resting on the armrest.

I don't have a grammatical term for the red clause.