1. "Sit down to" doesn't have any exciting or unexpected meaning to it. It means sit down to do something. In this case, it means sitting down and getting on with writing.
2. "between hand and page" means the hand was struggling to put something on the page. All you need to do in order to write is use your hand to write something on the page but there's some sort of error and you just can't do it. Writer's block.
The "intellectual Gobi" is a metaphor (very nice, by the way). You know Gobi is a desert, right? A vast, empty, lifeless space. So it basically refers to intellectual emptiness, lack of inspiration.
What book is this? I'm starting to really like it :)