I used a Lokar floor mount brake, which may be different from what you've described, but I'll try to help. I'm not clear as to the grommet you refer to. On my set-up, the cables are under the car and do not pass through any part of the body. Admittedly, the handle is close to the floor when down. (See Interior Pic Link)
At the handle end - my cable ends went into a block with 2 holes with a set screw for each cable. (See Lokar picture)
On the axle end, I was attaching to a Ford SVO set-up (off a 1999 Explorer). There I used a combination of stock Ford and Lokar parts, until I got the right return spring pull and the Lokar cables were properly retained by the stock e-brake hardware. I used the stock Ford springs. Cutting the Lokar springs did not work for me, they didn't have enough pull.