Shaker,
You won’t break the 6.6, just squash it when you sit on it.
If the 6.6 is in the 400, that’s more like it, still a bit light for you but not too bad. 7.2 would be better. see how it feels.
If you are REALLY 130kg id use the 10kg in the 650. It’s a fkn big spring for the DR and I really only use it for the biggest heffalumps. Either spring is arrr $150 OB price.
Hard to know what’s in the shock, BUT i do run the rebound dampening WAY harder for these big springs to prevent PDS (pilot discharge system) type crashes when the stored energy in the spring tried to launch you into sub orbit.
Shock rebuild/revalve $220 plus seal/bumpstop/parts if required. DR650’s are pretty good, nothing much goes wrong.