You ain't gonna get there that way with 4% accuracy.
Use the optocouler for isolation. You can get them all the way up to 2500volts iso quite cheaply.
Then use a V-to-F on the one LED side and an F-to-V on the other side. You can pretty readily get down to 1% accuracy.
OR, a faster easier way, is to use a screen capture utility, and capture a picture of the Scope with its data, and paste that into word as a picture object.
Ok, I will give you the first step. Use a "To Workspace" block to get the data to a variable that is globally visible.
Now, save only the waveform part of that variable to a new variable for export to word.
I have had good experiences with Gennum chips. They are a little known company with good products. I haven't used the ones you are talking about, but give their apps guy a call and ask him to tell of some customers using those chips.
Take a look at this website...
http://home.earthlink.net/~ojmsmith/indexd.html
You can get a copy of his patents and figure out what he is doing. It is very simple and very elegant. Very worth considering.
Let us know what you decide on.