In Tree of Peace, measure 15, I would use an in-accord with transcriber-added rests to show the crescendo beginning on beat 3 and ending after beat 4. In measure 18 an in-accord isn't necessary. The decrescendo can come before the first note and the piano before the quarter rest.
In 1941, the lower parts should use an in-accord to show the decrescendo beginning on beat 3. A termination of this decrescendo would not be necessary.