Belle- Is there any way you can bring up the school's failure to administer the IEP correctly to the district or state? Frankly if you are willing to pull him out anyway, it's not like burning the bridge will hurt you too much and then, maybe, other IEP students will receive better instruction/care. Just a thought . . . I also understand just wanting to be done with the entire situation.
Nevertheless, good luck with all of your decisions! I hope you can get some relief and peace once all of this is behind you (at least temporarily!). Your DS is fortunate to have someone fighting for him!!