Regarding your partner's snoring, have you tried sleeping with earplugs ? I use them to sleep when my wife snores. They help a lot.

Regarding 5-HTP, taking it is like a diabetic taking insulin. If your body is not converting L-Tryptophan to 5-HTP in adequate amounts, you will be lacking in serotonin. Taking some can make up for that lack. If it makes a difference, you have your diagnosis of a need. The risk of an overdose is minimal if the dose is increased in small increments.

I lived with high serotonin levels due to a prescribed and needed high dose SSRI for 14 years. The 100 mgs of 5-HTP works far better.

btw, I go to bed at a different time than my wife so she can be fully asleep before I get in bed so I do not get focused on the sounds of her before she is asleep. She also gets stuck focused on my breathing because I am prone to apnea. It is not ideal but it works.