Yeah, the issue comes in that the input values for LFO speed output uses some sort of exponential type of curve, but doesn't seem to be the right curve required to double frequencies per octave (ie: doubling per 12 input values, 24, 48, 96 or something else).
I remember I experimented with this a couple years back, trying to do what you're doing and document it in the appendix, but I couldn't figure it out what the curve the LFO speed uses, or if there's a way to accomplish the LFO to key track like key frequency.
I would be interested to know if anyone has figured out what the LFO speed curve is, or if Seq devs have some info that could be shared.