4th.
Yeah, I know what you're saying about the lower you are, the less shock travel you have.
So you height should be like this:
Sleeve-to-collar + spring + thickness of collar. (assuming that the spring perch on your shock and the upper mount is all the same as everyone else's
)
Travel is shock body to bumpstop, right? So if you're lowerred, that mean the bumpstop is going to be lower (closer to the shock body), since the shaft is compressed. But unless your shock is fully compressed (bottoming out on your bumpstop), the bumpstop shouldn't affect your ride height.