1) It is *not* a trust agreement, nor does factcheck.com have the title correct.  It is titled "Gift Administration Agreement," not "Gift Trust Agreement" and does not create a trust (a separate legal entity) to oversee the stock options.  Instead, it is an agreement granting power of attorney to someone (whose identity we don't know) to exercise and sell the options for the benefit of the specified charities.  There is no requirement that the stock be sold by any specific date.

2) While it says in section 8(e) that it is irrevocable, section 8(c) goes out of its way to state that the agreement creates no legal rights for any of the charities.  And section 7(b) provides a mechanism for the agreement to terminate without having completely donated all of the stock (the agent needs only to be in breach of the agreement, which could easily be arranged).  Section 7(a) might also provide a way out, if the agent resigns, and no new agreement is signed.

3) I see nothing in that document that indicates that this wouldn't create a huge tax deduction for the Cheneys.