Goal: I would like the LEDs to light all the way (1-8) with the speed of the servo and reverse as the servo slows down and reverses.
Firstly, I would use an odd number of LEDs so that the centre one is lit even when the servo is stationary. In fact, it would always be lit. Instead of looking at the speed of the servo, it would be easier to determine how far away from it's target position it is. You know the position it's in (= the current position). Lets call it curPos. And you know the position you want it to go to (= target position). Lets call it tarPos. If curPos < tarPos the servo will be going forwards and if curPos > tarPos the servo will be going backwards. tarPos - curPos will give you the distance to be moved forwards and curPos - tarPos will give you the distance to be moved backwards, so you can calculate the number of LEDs to be lit. You'll need to update curPos as the servo moves nearer to the target position. When curPos == tarPos all the LEDs, except the centre one, will be off. You could use a tricolour LED for the centre one and have it showing white when the servo is stationary and red when it's moving.
If you agree that that is the way you want it to go, we can start thinking about the programming.