Should I send one final goodbye for closure, or leave things as they are?

My relationship recently ended badly, and I'm conflicted about whether to send one final goodbye or leave things where they are.

My ex has diagnosed BPD and was also physically unwell towards the end with a sinus and chest infection. Our relationship had become difficult for me. He could go from being very loving and affectionate to angry, cold or irritable, and I found myself shrinking and walking on eggshells because I didn't know what might upset him. Earlier on, he would usually try to repair things afterwards, but towards the end that stopped.

His communication also became very inconsistent. He would say he'd call or update me and then disappear for days. There was also a woman messaging him "hey baby" and saying she missed him. He told her he had a girlfriend and showed me, so I don't know that anything actually happened, but combined with everything else it made me anxious and confused.

I tried to communicate what I needed. I wasn't asking for constant contact or reassurance, I asked for basic communication, openness and respect, particularly if he needed space or plans changed. I also asked him directly whether he wanted to break up or needed space, and he said no to both. But afterwards he continued becoming more distant and sometimes spoke to me as though I was a nuisance that he could barely stand. It left me feeling humiliated and close to tears. I couldn't reconcile what he was telling me with how he was treating me.

Eventually I told him I needed to step back because of how he was treating me and asked whether his feelings had changed or there was someone else. I told him I'd rather he just be honest with me. His response was basically, "Sure. I won't contact you." When I tried to understand what that actually meant for our relationship, I never really got the conversation or closure I was looking for. He just shut me down and acted as though he didn’t care.

I became extremely hurt and angry and said things that were harsh. He blocked me afterwards.

I've spoken to my therapist today, who told me what he did wasn’t okay but also helped me understand more about BPD and what someone struggling with it may be experiencing internally. It's made me look at the ending with more compassion. If he genuinely was struggling mentally while also being physically sick, I don't want to be cruel to someone who may already have been having a difficult time even if they were acting cold and indifferent towards me.

That doesn't mean I think everything was my fault or that I want the relationship back. Some things genuinely hurt me, and friends I've spoken to have said some of his behaviour came across as manipulative or controlling. Ultimately, I don't think the relationship was healthy for me.

I also recognise that it wasn't entirely one-sided. I have my own anxiety and fears, I made mistakes, and there were things I could have handled better. I can acknowledge that some of his behaviour towards me wasn't okay while also regretting how I reacted when I was hurt and angry.

I've written one final goodbye that acknowledges my part without taking responsibility for everything that happened. I don't want to reconcile and I'm not expecting a response.

What I'm struggling with is whether sending it might give me some closure after such a painful and confusing ending, while also allowing me to leave things with kindness towards someone I genuinely cared about and who may have been struggling more than I realised. But he blocked me on WhatsApp, so I'd have to contact him via normal text, and I'm conscious that could be crossing a boundary.

I'm also trying to work out how much of my urge to reach out is actually my anxiety and fear of abandonment talking. I have a strong instinct to repair things when there's been a rupture, and I don't know whether wanting to leave things peacefully is genuine closure and compassion, or whether I'm struggling to tolerate an ending that I didn't get to resolve.

If you were in my position, would you send one final goodbye to leave things on a kinder note and perhaps get some closure, or leave things where they are? How can you tell the difference between genuinely wanting to show kindness to someone who may be struggling and anxiety or abandonment fears making it difficult to let an unresolved ending stay unresolved?