Sorry for the delay in getting to your question, Do you still need help on this?
Ok if the filter isnt unscrewing then theres somthing stuck in there.
What i do is hold the filter with a pair of pliers and then try and unscrew it and quickley tighten it up again.
Do this a few times as it can dislodge what ever it is in there.
Then try and unscrew it and see how it goes from there. Fingers crossed that does it.
But if it wont unscrew still then you need to pull the washer out and lean it backwards against a wall and have someone hold for you.
Then look under the washer and hopefully it isnt a sealed base and you can access the pump under there.
You need to remove the black hose on the pump and then you can clear what ever it is in there stopping the filter from turning.
Try that and see how it goes and let me know.