Pronoun + ing

1. She couldn't ignore him speaking directly to her.

2. I was sitting in front of him staring at me with suspicious eyes.

3. I didn't want to continue the talk with him ignoring my words.

4. I don't want to be with him always begging me to lend him money.

5. During class, the teacher shouted to him talking to his classmates.

Q1) Are all the sentences grammatically correct, natural, and unambiguous?

Q2) In each sentence, what does "~ing" refer to? I think that "~ing" refers to him in each sentence as shown below. Am I right?

In 1, "speaking directly to her" is referring to "him"

In 2, "staring at me with suspicious eyes" is referring to "him"

In 3, "ignoring my words" is referring to "him"

In 4, "always begging me to lend him money" is referring to "him"

In 5, "talking to his classmates" is referring to "him"

Q3) In each sentence, must there be a comma as in "She couldn't ignore him, speaking directly to her", because "him" is already specified? Or is it okay not to add a comma to leave the "~ing" part restricting the information of "him"?

Q4) As a side question, which sentences below are grammatically acceptable if "who was" is used?

(In b1 and b2, there is a comma in front of "who")

a1. She couldn't ignore him who was speaking directly to her.

a2. I was sitting in front of him who was staring at me with suspicious eyes.

b1. She couldn't ignore him, who was speaking directly to her.

b2. I was sitting in front of him, who was staring at me with suspicious eyes.