An estranged couple decides for a last-chance counseling retreat in a forest just to meet a therapist who reveals their secrets that should rather have remained buried

But that goes back to the original problem, they shouldn't be confronting each other, they should be working together to survive. They are estranged and they disagree on everything. They have to learn throughout the ordeal how to work together.

An estranged couple decides for a last-chance counseling retreat in a forest just to meet a therapist who reveals their secrets that should rather have remained buried
-----
This re-write gets away from what makes you story interesting. You have a bickering couple going to therapy in the woods, they are attacked by a madman and in order survive they have to do the last thing they really want to do; work together.

The irony of your story is, being chased by the madman does what the therapy couldn't, it gets to work together.

This logline version gets away from that.

This logline kills it!!!