Asonderu
If you are convinced that your ISP spies on you, and believe it to be a mere possibility that Mullvad doesn't, then I would get a subscription ASAP to mitigate risk.
Mullvad is also not based in the country your from (unless youre from Sweden) so even if your country wanted to, they couldn't force Mullvad to hand over data.
The police (before the raid) know about as much about Mullvads data as the average privacy aware person. Under international pressure, Swedish authorities will absolutely give Mullvaf a visit, even if mullvad claims to have a no log policy. This has happened to multiple VPNs that got exposed in that way for a fake no log policy.
Lastly, Sweden is a democratic state , and while they may spy on people, it would raise concerns if they fake the result of a police finding