Manifesting in Fromville and how to escape from there
S04 E05 confirmed that fears can be manifested into reality in Fromville. The other aspect of it was revealed too - hopes can also be manifested. That is how the child Tabitha saw was able to defend herself against the dolls - by imagining a weapon that hurts them.
It is rather obvious this same mechanic enables everyone to escape from Fromville too. Ethan has manifested a way out of there by believing it follows his favourite book's storyline.
Mainly children seem to be able to manifest hope, because of their pure minds.