Can anyone suggest anything that might help
Yes. Recognise that it wasn't your fault. There are 2 things to consider here. The first is that the things he said are his opinions, not facts about you, or who you are. They are the opinions of an unfaithful, rude, insulting, disrespectful person who clearly doesn't have any intention of being kind to you. Why did he have to say anything at all? Because he needed to hurt you, and he knew how to do it. That's why these things have hit home; he knows your insecurities, and has deliberately hit you where he knew it would hurt. Ask yourself if you really want to be respecting the opinions of this kind of person, and if so, why? This is an internal job, for you; it's not about him.
The other thing is that even if all those things are true, he is still the one at fault. If a person is bored in their relationship, it is their responsibility to communicate this to their partner, in a non-hurtful way, and try to find a way to make things more interesting. If a person is no longer attracted to their partner due to physical changes, it is their responsibility to raise the issue, in a non-hurtful way, and try to find a way that both partners can deal with, to work it out.
His way of leaving says everything about him, and nothing about you, except that you have been an open partner with him, and allowed him to see where your vulnerabilities are. It's not your fault he's preyed on that.
Think about the most confident person you know (in person, on telly, whatever) and imagine them dealing with this. Imagine them saying 'You're trying to blame me for your cut and run, you man-child? Stick it in your pipe and smoke it. I've seen who you really are and it's a horrible picture. I will never look back.' Or however they'd be likely to phrase it. Get this voice in your head whenever you feel self doubt. Because self doubt is your enemy here.
You KNOW you did nothing wrong. You know it. Hold onto that. It is your truth, and more important to you than anything he, or anybody else, says. Dignity is your friend, and, often, silence in the face of insults is the friend of dignity.