Some writing questions

<ol>
<li><p>The board members along with the chairman were planning a series of speakers to lecture on different dividend plans for their employees.
Why isn’t “their” a pronoun reference error? Isn’t “their” in this context ambiguous? </p></li>
<li><p>I found that “nowhere near” and “not nearly” are not equivalent. What are the differences and in which cases do we use them?
E.g. The parents realized that they had brought nowhere near the number of chaperons required to control the children.</p></li>
<li><p>There is a golden rule that one should never use “due to” in the beginning of a sentence instead of “because of”.
“Due to” is adjective.
Here in this sentence isn’t “due to” used as an adjective? Is this sentence correct?
His not studying and not attending review was due to a prolonged sickness.</p></li>
</ol>

<ol>
<li><p>No. Not at all. Who but the chairman and the board members could the employees belong to? </p></li>
<li><p>Hmm. This is not technical, but my gut feeling. Nowhere near seems like it should refer to things that are not numbers (You are nowhere near right) while not nearly can more easily refer to quantities (Those 2 cookies are not nearly enough for the 5 of us. )</p></li>
<li><p>I never got the “due to” rules. They seen stupid. No help from me there.</p></li>
</ol>

<p>re these rules like legit?</p>