In my opinion, there is no safe place, but I can prompt you to accomplish these achievements as quickly as possible :)
Below is my suggestion.
The best place to collect Broken Dreams is near depot and temple. You can collect them while standing afk in protection zone.
And one of the better places which is located at here :
Running to the NPC for the road you can find a lot of these glowing trees from which you can collect Broken Dreams.
Half-Buried Face you will find in these places (marked on the map with a skull):
In the place marked with red circles there are a safe spot on the stairs.
My way is that you run quickly to every face, use this energy bomb or energy wall in critical situations. By the face I stand on the energy bomb to be able to quickly recall the butterfly. In this way I achieved the achievement very quickly. Unfortunately, we can carry out missions every 2 hours so it is time consuming after all.