Oh, I like the plot you are building here. :)
If you choose to continue, I for one will definitely read... and beta, if you'd like. :D

As for the characters, I don't think you are far off on either of them. Of course, it wouldn't hurt to occasionally toss in a few more of the common Ten and Donna phrases or gestures. But really, in the end, I like your take on both of them. Donna's taking no lip from the Doctor but still supporting him when she knows she must.

I say keep it coming!