I ran 115 with stock link and now 105 with gen5 link (110 is too stiff), 83kg.
You ditch your custom link that puts rear low and creates squat problem (low swingarm angle).
Flat swingarm angle is bigger problem that wrong damping or spring. To get that right measure swingarm axle and rear axle height from ground. The diffence must be at least 118mm (121mm creates angle of 12 degrees).
Use gen5 link and you should ride more or less ok with existing shock as is.
Gen5 stock has higher seat seat height, check that out, maybe you are sitting too high.
I tried once extra chain link like you have and that made steering less responsive. I would say use stock chain unless 44T rear sprocket.
Shorter wheelbase is better for tight tracks. To keep stock chain I went 15T at front.
Watched your riding video, while your base speed is good, there is room to shave many seconds easily.
I think if you go to S1000RR you can turn few seconds faster and hit same limits, good take some racing instructor training and you could improve 10 seconds.
I noticed that you often go through corner with throttle closed.
It may be a bad habit or you feel unconfortable cracking throttle open much earlier (mid corner), not well anchored in bike, supporig weight on bars mid corners etc.
Fast riders open a crack quickly after braking to create stability. There are many levels of throttle: just to tension the chain (no engine brake, bike still decelerates), maintaining speed, little acceleration to transfer weight away from front and prepare for pickup rollon.
In fast corners it takes big amount of roll just to keep the bike from slowing down.
Your flick rate and slow pickup suggests that you are not consciously giving proper steering input.
Many fast hobby riders are not steering before brake is released, try to start pushing inner bar at second half of brake zone, bike does not lean much while brake applied, but as you release brake it drops quick without drama.
At corner exit a beginner is coasting forever to the outer curb and starting to accelerate suddenly there or picking up bike a little and accelerating hard leaving lean angle the same (ca. 35deg).
What racers are doing is different: the line after apex is such that it is possible to finish turn in the middle of road, but right after apex I pull hard inner bar to pick up quickly and roll throttle smooth and hard.
This causes smooth shock action too, no sudden weight transfer or gripp drama.
Try this: stay in full lean angle one second longer than usual, then steer hard to drive directly to outer curb, next time roll throttle during pickup and try to hear/record motor rev. increase what should be nice linear revving.
This way you make use of 1000cc power compared to 250cc.
Gen4 race: high spec.
Suzuki GSX1300R Hayabusa 2013: stock.
Kawasaki KX450F 2016: love it.