On question #2. If there is no extra cutout exists other than the one on the cowl, then probably yes, you need to open it up more. It should be at least the same size as the current cut-out.

On #3. you can install an sleeve tube over the nylon rod and anchor the sleeve tube somewhere inside the engine box of front of fuse with a piece of 1/8 plywood. The rod should slide freely inside the sleeve tube.

On #5. You can install two anchor points on the firewall (near the bottom with 1/4 plywood). Install two blind nuts on the plywood (facing down). drill two holes on the bottom of the cowl so that bolts can pass through the holes and screw on to the blind nuts. Another option would be to open up the cowl at the proper location so that you can directly pass the bolt through the cowl with a long hex allen ranch.

Hope this helps.