[Maker]

Hey, so currently I have DT 990 Pro, but the clamp is too strong so I´m going to sell them and try out DT 990 Premium, becouse i really like DT 990 sound signature. So my question is, should I go with DT 990 Premium 250 ohm or DT 990 Premium 32 ohm? It will be running on Fiio E10. Thanks

 

[NA Blur]

The 32 Ohm version has a high enough impedance that there should be plenty of damping.  The 250 Ohm version adds some concern regarding voltage / current from a given device which is why I think the 32 Ohm version is the safer bet.
 
In response to the excessive clamping force you may want to try placing the headphone over a full-sized tissue box while they are not in use.  I did this with my ATH-M50 headphones and made a large difference.  Typically it takes a week to fully relax the fit.