Hi,I am running the same conversion,but have only done about 500 miles!
So far I have discovered that,as you have,you have to change down earlier in the higher gears,I was expecting that,the dmf absorbs the vibrations,without it you just gotta change gear!It's like proper driving again.
I noticed a slight loss of low down torque,again I think down to the action of the dmf and it's springs,possibly,this actually makes low speed driving smoother as the accelerator movement now corresponds to the amount of acceleration.
I like the more positive,direct feel of the clutch and the fact pulling off is way smoother than it used to be(my dmf was absolutely §hagged . . . .as was the clutch!)
I think my gearbox is tired,however,(slight crunch between gear changes and a slight whir when in neutral,that the rattling old clutch was disguising!)so it will be interesting to see how long it lasts.
As for the damage this mod may or may not cause,from a personal viewpoint,if your driving style changes slightly to take into account the changed characteristics I can't really see that the longevity of the mechanicals will be compromised.If you do traffic light drag racing,then you may break something,but you would with a dmf fitted,too I think.The thing that seems to be working harder in my bella is the engine mounts,they seem to be a little soft allowing a bit of engine movement.Maybe they are the weak link?
I have heard the stories of crankshafts breaking,but from the research I did,this usually came from people with a vested interest in dual mass flywheels or was third or fourth hand,ie a mate of a mate had a friend kinda thing!
If my crank breaks tomorrow . . . . .