Thank you for the deatiled reports!
I think the Text to Tag function is currently not useable for the amount of files and lines you're working with. Even with 5K lines, there is a significant UI freeze, while Mp3tag tries to split the pasted text into separate lines. I've made a note on my internal list and will try to improve this with an upcoming version.
As for the secure bookmarks issue: did you try opening your home directory via ⌘O and then ⇧⌘H to prevent future issues? You can also cancel the reading process, because it would probably take some time.