Ok please contact me by PM if you need further help but here we go:
Use the fisheye, don't even think about the 16-35.
You need a panoramic head, rent one like a Nodal Ninja or a Manfrotto SPH 303 plus or similar.
Use the camera in portrait mode, shoot 6 shots with the camera angled 30 degrees up and 6 shots with the camera angled 30 degrees down.
Find the entrance pupil of your lens at home using a near/far objetc, google for "finding nodal point" the term nodal point is not correct, should be entrance pupil but you need to google nodal point because people use the wrong term.
This will give you plenty of overlap to compensate for parallax errors and you wont need a sepparate nadir and zenit shots.
Remove the tripod and shoot nadir and zenit shots anyway.
To remove the tripod from the pano there are several methods. Google, ask for help, write me, send smoke signals...
About software PtGUI is very good, try it! Hugin is also excellent and is free.
Hope it helps