REM in a partner can definitely be terrifying. When my husband was first diagnosed about 10 years ago, one of the things mentioned was this can be an early indicator of possible Lewy Body Dementia years later. Many people do not end up with LBD. We are some of the unfortunate ones, he did finally show signs of LBD and was diagnosed about 18 months ago.
This is ironic - as LBD progresses, the REM regresses! He also takes Clonazepam and Melatonin (pharmacy grade from a compound pharmacy the sleep doctor recommended). If I were to go back 10 years, I would get a second Neurological opinion and encourage a brain MRI for a base line.