I have to tell you that your frame is an unbelievable beauty!
To solve the steering-problem: Could you get hold of another triple-tree? To me it seems that the stanchions and the steering-bolt are (nearly?) in-line. I'm more used to stanchions that are a bit ahead of the steering-bolt. An arrangement like that would give you more space from contact to contact. I know that finding another triple-tree isn't easy. Maybe your fork is used in several bikes, perhaps you find a combination that fits.
Keep up that superb work! Usually, I'm more into singles and twins, even on the road, but your project strikes me like lightning.
Kind regards, Bambi
'Find me kindness, find me beauty, find me truth ...'
(Dreamtheater, Learning to live)