I certainly know what it's like to be in your shoes, losing sleep, feeling depressed, searching for answers. I can and do truly empathize with your relationship struggles. And honestly, I still struggle with this (though to a lesser extent than in the past), and certainly all my relationship problems are not solved. However, my relationship did truly experience a significant improvement. So perhaps my experience / research is of some value to you and others that are in a similar situation. I'll go ahead and share a few more pertinent thoughts / resources below, but it won't be comprehensive. If you'd like to discuss this more comprehensively (I don't want to share too many personal details here) I'd be happy to chat with you via email or phone. You can email my throwaway account to get my contact info. My throwaway email account: barndoor16@protonmail.com

I think you touched on the root of the one-sided empathy situation with your SO and most likely also your broader relationship issues: incompatible attachment styles. After much research / reading and therapy, I eventually identified this as the root of my own relationship issues as well. Essentially it boils down to this: a person with an insecure attachment style is poorly matched for a person with an avoidant attachment style. I highly recommend reading the following book on this matter:
"Attached Are you Anxious, Avoidant or Secure How the science of adult attachment can help you find – and keep – love by Amir Levine and Rachel Heller". I also recommend reading Gottman's book "The Seven Principles for Making Marriage Work" (Gottman doesn't really utilize the attachment styles model but his model is effective for relationship issues nonetheless).

Regarding how to talk to your partner about this, the optimal approach is in fact certainly much more nuanced than "be direct". You need to take care not to make your partner feel criticized, as this will trigger defensiveness, causing them to become more resistant to making changes. Generally, using "I feel" statements is a good approach but it can be tricky to implement well in practice. Also, you certainly don't want to make your partner feel the relationship is threatened / communicate a threat, unless you sincerely feel you're tired of trying / progress isn't being made / you've exhausted all other approaches. With I statements, it's possible to communicate that an issue is very important to you and your happiness in the relationship without making your partner feel excessively worried that the relationship is threatened. In particular by making it clear that you're not looking for immediate changes / perfection - that you're willing to work through it with them. And there's certainly much more to communication - it's a deep topic.

I think it's also important to note that attachment style / relational incompatibility is a matter of degree. As you'll learn from the book I recommended, attachment style is quantified on a four quadrant spectrum. If you're only a little insecure and your partner only a little avoidant, then your incompatibility is probably more workable. So I would certainly recommend using the attachment style assessment tool to gauge the degree of your and your partner's attachment style incompatibility. So while it will certainly always be difficult being in a mismatched attachment style relationship, it is possible for both partners to meet closer to somewhere in the middle and have a mostly functional relationship, through a mutual deep understanding of the mismatch and a sincere willingness to modulate your respective behaviors and expectations. However, if eventually you observe that your partner fundamentally lacks a willingness to make any significant changes to their own understanding and behavior, then I agree with the other poster in this thread that leaving the relationship should be seriously considered. But from what you've shared so far it sounds to me like you've not yet reached that point / haven't exhausted all your options. That said, the decision of whether to keep trying to make the relationship work or to give up on it, also depends on how much you've invested in it already. A long marriage with a kid (my situation), warrants trying harder to find solutions, putting up with unmet needs longer, and generally being more patient. If you don't have much time invested in your relationship then it may not make sense to keep banging your head against the wall for years (as I did). In which case you may want to set a more reasonable time limit on the order of months (keep this to yourself of course) to see if there's sufficient progress.

I also highly recommend seeing a personal therapist as they can provide an alternate source of empathy to you for your struggles so that you're not totally reliant on your avoidant attachment style partner - this was invaluable for me personally. Couples therapy was also helpful as forum for discussing relationship issues with my partner. It helped lend more weight to what I had to say, so that they took my stated issues and my analysis of the cause and solutions for the relationship problems more seriously.

Hopefully this is helpful to you and anyone else in a similar situation that comes across this post. It's really difficult to understand the cause of one's relationship problems and to find solutions because there's just so much information out there that it's hard to separate the wheat from the chaff. Not to mention that you're doing all this research under the constant drag of feeling emotionally distressed / depressed. And although therapists are very helpful, in my experience, without extensively researching / reading on your own, you're unlikely to cultivate a deep enough understanding to work through to a positive outcome for a fundamental relationship problem such as an attachment style mismatch. It's a real struggle and I really wish there were better resources to help people that are dealing with relationship issues and mental health issues in general. In any event, best of luck to you, and as I said feel free to reach out if you want to discuss this further.