How many attacks do I get with Two-weapon-fighting and a high BAB?

[Shadow13.com]

If a character has a high BAB, it allows him to make an extra 1-3 attacks as part of a full-round action.
The two-weapon-fighting feats also allow you to make additional attacks.

I'm confused as to how you would calculate the total number of attacks.

Let's suppose my BAB is +16/+11/+6/+1 and I have the Greater Two-Weapon Fighting feat (with a light weapon in my offhand).
Would I be able to make a maximum of 7 attacks?

This is how I'm calculating Attack bonus. Is this correct?
Attack 1 (primary): BAB +16, -2 TWF
Attack 2 (offhand): BAB +16, -2 TWF
Attack 3 (primary): BAB +11, -2 TWF
Attack 4 (offhand): BAB +16, -2 TWF, -5 Improved TWF
Attack 5 (primary): BAB +6, -2 TWF
Attack 6 (offhand): BAB +16, -2 TWF, -10 Greater TWF
Attack 7 (primary): BAB +1, -2 TWF

So my attack bonuses would look like this: +14/+14/+9/+9/+4/+4/-1

Since I'm not making an offhand attack after my final primary attack, does the -2 TWF penalty still apply to that final primary attack?

Also, if I choose not to attack with TWF at any point, would the -2 penalties go away?
For example, let's just say that I only wanted to make an offhand attack once:
Attack 1 (primary): BAB +16, -2 TWF
Attack 2 (offhand): BAB +16, -2 TWF
Attack 3 (primary): BAB +11
Attack 4 (primary): BAB +6
Attack 5 (primary): BAB +1

[Name Violation]

with twf, itwf, ang gtwf you can make up to 7 attacks.
if you make at least (or plan to basically) 1 attack with the off hand weapon, all attacks take the -2.

so the to figures are correct