I'm in a similar place with my dads stuff. He died 6 years ago. I have every piece of his clothing, and lots of his personal stuff too.
I have been able to keep it as we have had the space, but now DD is here and has more stuff than the Queen of Sheba it has to go.
I know it has to go, but I can't help you with how as I havn't got that far myself. I think it will have to be a 'rip the plaster off' type thing and just clear it all in one day.
For the things you have you could make a scrap book/box.
Cut a sample of the bed linen and a photo of the whole thing and build up a scrap book.
For things like the cutlery could you get rid of yours and replace it with you DM's?
I think it probably is a comfort blanket for you, mine is, and although I do still have a lot of family, I so desperatly miss the comfort and security of my DF, and the safety he gave me.
You could start a bit at a time if you can't face it all. Start with the things with least emotional value, the curtains and linen etc. Then leave it a while before moving on to something else.
My dad died the day I signed for my first house, so I had use for all of his furniture and house hold things, but I think now if it were to happen, I might contact some refuge/shelters and offer the stuff to people in need - thinking along the lines that helping some one who is having a bad time and making a difference might 'take the edge off' my feelings of letting go.
I havn't been much help have I!