Multivibrator VCO Tuning help

[Proschuno]

So I've been working on this multivibrator VCO for a long time now, and all of my efforts have been trying to get this to follow a volt/octave response. So far it actually has an exponential response to input voltages, even if I just tie the pot directly to the grids, so I'm thinking I wouldn't need an exponential converter. I'm wanting to know what you would suggest to do to get this to have a volt/octave response. I'm thinking I should replace the 330K resistors with pots; I just simply don't have any, I keep burning them up! I'm going to order a large batch of them from Mouser very soon! Any other suggestions would be greatly suggested.

It doesn't exactly have to be all tube based, which kinda violates the point of this forum, but since it involves tubes (which are responding to control voltages clearly), I figured it would be worth a post.

I'm using a 12au7 as the multivibrator tube (triodes on the inside), and a 6sn7 as the control tube (the triodes on the outside). And the caps are 10nF, and all the numbers with K's are resistor values.