Kori Quatermass

I got a used replacement fork for my favorite bike (that had a bent
fork at the steerer tube). It has a different curve in the fork blades
but the rake ends up being very similar to the original fork. It does
have a slightly shorter axle to crown distance.

Besides the old fork being bent, it rode straight and stable. The new
fork is VERY shaky. I can barely take one hand off my bars without
losing control. Whereas with the original fork I could bike to school
while eating my lunch without any problems.

Any ideas why this is or how I can fix it? I would like to replace the
fork with a 1" threaded fork that will be as stable as the original
but unbent. The market isn't exactly flooded with 1" threaded forks
and I have no way to know if a new one would help the twitchy factor.
I have also considered taking the original fork to a frame builder to
get a replacement. (I am kinda attached to this bike). I also wouldn't
mind another mechanic's opinion on my original fork. I was told it
wasn't safe, salvageable/able to be fork doctored (yet it rode fine?).
Maybe I could just get a new steerer tube or it even?

It is my FAVORITE bike and I would appreciate any ideas, input, or
shop recommendations that could help me! I figure there has to be a
mechanic, bike nerd, or frame-builder in the mix who has some idea. I
included photos of both forks in case it is something really obvious
that someone would notice in a photo.

Thanks so much,
Kori and the valentines bike

before
http://www.flickr.com/photos/korimatiessa/43203093/in/set-848595/

after
http://www.flickr.com/photos/korimatiessa/3779673125/in/set-848595/
http://www.flickr.com/photos/korimatiessa/3779678447/in/set-848595/