Some
tweaks done just now after dinner. Take it for a spin.
Improved full scale swing to 6Vpp
Offset pot can exceed 6V tho since you specified a 9V bat. That can be fixed if needed or just adjust pot.
Coarse flap per sec. (fps) has a 50:1 range down to 15 sec. cycle for show N tell
Sawtooth defined with fast up flap regardless of flap rate or up to 1/3 sec cycle for almost 50:1 range
Fine fps is just for 2:1 range control and fine tuning.
So coarse can go from stop to full speed quickly
and fine can adjust 1 to 2 fps or 1.5 to 3 fps. for example.
YOu can increase Vpp to exactly 6Vpp by reducing 70K by a few percent with 1M in parallel but much lower and it will stop oscillating. when it exceeds hysteresis.
This also depends on saturation of OpAmp with ~8V out and battery level, so not perfect yet. ( perfect would use a 5V reference like 78L05)
Similarily if Coarse is brought to minimum it will exceed hysteresis and stop flapping and slowing drift to near null.
Plastic film caps will give the best performance over ceramic. for long time constant.
Note 5 channel sliders on right side . Simulation speed, Current (disabled) and 3 Pots.
Values can be scaled to use all 10k or 100k pots linear or log.