Re-reading them will only tear off the scabs covering the wounds,as mentioned, shred or burn them....

If you can, write it up as a sort of abridged family history, that you and your sister can share.
If you or your sister have children, they will appreciate it, and not having had to live through it, will not be traumatised, simply motivated not to do the same. Whilst you're about it, write candidly about your childhood and early adult period.
Then dump any stuff that has no sentimental value!

I am so sorry for your experiences. That is so difficult for you all. Sometimes people cannot let go. Its dreadfully sad and very damaging. I won't give advice, just my very best wishes. Eventually you will know what is the right thing to do.

Should probably ask your mom what she wants done with her stolen things. If you don't want to talk to her dispose of it.

My credit union has Shredding Saturdays several time a year. Take it to be shredded and think no more about it.

IF anything positive can be gained by reading through them or certain other family members reading through them (understanding? closure?) maybe... If only heart ache or dredging up pain of the past lies in it, discard.

Get rid of it. You don't need that negativity hanging out in your life.

The past, learn from it and let it go. Personally, I would have thrown in the trash after looking through the stuff. Just sounds like a lot of bad memories.