Still, if you were the Fighter, what would you have done to help ensure victory?
Not be large. Crawling through the rings would have been one hell of an "lol in your face". Hell even shooting arrows (with a glued antimagic torc) into the rings would have been far better than slamming face first into the Prismatic Wall too. >.>
First rule of casters is they need LoE, control the LoE and you control them. Like the Rod there prevented a huge chunk of spells, and being Splatbook-allowed Fighter his Charge damage should have auto KO'ed the Dragons while they were Flat-Footed allowing him to gain some control of the rings, in fact with the caster being Incorporeal the fighter would dominate the control.
I'd think picking up the Wall of Iron (10x10x?) is a concept to consider as well but I'd have to google weight and carry loads for an unknown Strength score etc. Might be feasible to transport it a mile into the air and drop it, if the Wizard doesn't leave it he rings out.
Lastly, rules on how to win mean the Wizard lost to begin with. Bag of Holding is an extra dimensional space, and unlike the Portable Hold, no exact dimensional size, entrance or exit (you always grab what you reach for there is no 'bottom') for all purposes, there no measurable distance between something in the bag and something out of it so nothing can ever be defined as within 1 mile. It doesn't matter that the Astral Projection was close by, fundamentally the Wizard exists in two bodies and therefor is always in a state of qualifying for out of bounds. Not that the issue of attacking the real one ever came up and could be easily removed. But theres a moral to the story there. Wizards never play by the rules.