Also having spring gain at 50% and the potentiometer at 45% means your spring gain is less than 25%. I'd say set spring gain to 100% and adjust the potentiometer to the spring gain setting that works for you while in the hornet.
I've never experienced any jittering when in the hornet using the autopilot. I wonder if any of the filter settings may be causing that. A screenshot do the whole configuration page help to see if anyone notices an unusual value there. And maybe a video of the jittering showing the stick movement and also the config page as it happens.
In the video I can't see any jittering on the stick. However... Can you hit control + enter to see the controls in the lower left of the screen? Basically I want to see if in DCS the stick is actually centered.
I get the warrning when trying to engage it to begin with, can't even get it engaged unless I add that deadzone. Will be happy if we can do this without a DZ.
Ok so then the jittering is the culprit for sure. Just for the fun of it... Does it happen if you put the potentiometer to 100%? Full spring force. No deadzone.
I read somewhere here of someone having oscillations with friction enabled. Can you disable friction, damper and inertia. And if disabling them fixes it can you enable them one by one to see if any of them causes the jitter?
Then some effect on telemffb may be causing the rumble and interfering with the AP. If I remember correctly I disabled the rpm effect on it or something like that.