If you have other work to go to then definately a good decision.
Have learned my lesson and would not be drawn into a situation like you describe again! Ends up taking twice as long as you thought it would and you end u seriously pissed!
Its a shame you felt you had to walk away from a big job but as you seemed to agree most of the points before hand then so many things where being changed or added to then either the price has to go up or walk.
Stick to your guns. I dont mind too much if the odd thing changes on a small job but on a big one like this it can cost alot of time.....and time is money!