Sat writing practice questions from bb! Help

<p>So I took the second practice test in the bb and I have three writing questions that I do not understand. They are all identifying sentence errors. Here they are:
(section 6) 26- mediators were standing by , prepared to intervene in the dispute even though both sides had refused earlier offers for assistance. I thought that the was no errors but the correct answer is the 'for' part. Why is that so?
28- neither ms. Perez nor ms. Tanaka believes that watching as much television as her son Sam does will lead to anything productive. Since the subject is singular I thought that 'her son' was correct. But apparently it's not.
29- an amateur potter herself, the accountant offered to help the artist e. his business accounts, complicated as they were by his unusual system of record keeping. I thought that the 'as they were' part was uncessary, but the answer is 'no error.' why is that so? Do indentifying sentence error questions ask you to remove unnecessary parts in general?? Ahh so confused! Help >.<</p>

<ol>
<li>correction: offers of assistance. </li>
</ol>

<p>You make offers of [what you’re offering]. You make offers for [something you want to get].</p>

<ol>
<li><p>Ambiguous pronoun - whose son exactly?</p></li>
<li><p>Taking out “as they were” could lead to the interpretation that was accountant’s help was complicated. Tempted to just chalk it up as an idiomatic usage.</p></li>
</ol>