Thank you! Both for the amazing resource, and the thoughts on my questions.
For the leeway, I've found a similar source that has half a point of leeway "in a topgallant gale" (force 4-5), a point under topsails etc. I assume this was measured when close-hauled.
About the sail blanketting, I think I exaggerated it at one point, since I wanted to get some penalty for having too much sail set before the wind. Now I think this is a matter of difficult steering rather than aerodynamic problems, so I will have another look at it.