The Bull of Minrathous in Dock Town near the Side Alley Bridge south of the Sanctum. In the Tidarion Tower (where you get the second clue for "A Hidden Hoard", where the NPC says "this new passage just opened up recently") there is a a blue barrier. There is a small ward behind some wood that you have to break, then Bellara can open the blue barrier. This one took me embarrassingly long to figure out.

Mother of Halla memento in the crossroads during Solas' memory The Labs Below. Will be missed if you don't get it during that memory as you can't go back.

>>2 I believe the confirmed number are 4 mementos and one care taker experience item, can never find a full guide

This guide is missing a lot of momentos. I found 6 in the Ossuary and it only shows 1

Docktown- During the smuggled relic case mission- 2 can be bought from the merchant right when you start(pillars of Kal-Sharok:Voice and A Fool and His Skull), another right when you go up past the closed chantry behind a closed gate that you have to jump into the opening (Many-Limbed Statue).