I had similar problem; I split my monolithic repo, monolithic-git, as follows.
1. When I did the git-svn, I ended up with git branches for each
project in my svn repo. I think I created these by hand, but I don't
recall.
2. To split project foo into its own repo, foo-git, from monolithic-git, I did:
mkdir foo-git
cd foo-git
git init
git pull ../monolithic-git foo
From then on, I worked in foo-git. Eventually, I pitched
monolithic-git. I suspect there's a better way to do this...others
will surely chime in.
dave h