IMP pairs.
The 1N opening can be on an average+ 11 count, but not any old drivel. It systemically includes all permutations of 4441 and 5542 distributions.
Your initial Stayman bid was consistent with a weak takeout into diamonds, so that's probably how P would read 3D here. X would be competitive.
Over the double, partner could have redoubled with good clubs. You don't have specific agreements about what a pass would have shown (incidentally, is there an expert standard here that would make sense for a weak NT?).