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.
Here :
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.