The Tojiro Shirogami 240mm gyuto weighs 7 ounces....so the 210 SHOULD weigh well less than your current Forschner.
However, do you know how to care for a carbon steel knife? This knife is carbon, clad in a very reactive iron. I would not recommend it for a complete carbon steel newbie.
If you're dead set on the weight issue, this is a good knife that weighs less than your current:http://www.chefknivestogo.com/fufkmgy21.html
Between the DP and the Shirogami, the Shirogami ITK knife is easier to sharpen....but again, the carbon thing.
A true yanagi is single beveled and purpose built to slice raw fish. If you want a purpose built knife, get, and learn to properly sharpen a yanagi.
Sharpening a single bevel, hollow back knife, is NOTHING like sharpening a double bevel knife. It's not that difficult to get the basics down, but mastering it is a life long obsession for some.
I would recommend a sujihiki, that's what I use for the things you mention.....plus it's great at other things.