Can anyone help with this?

[catisbeingsick]

I want to feel less responsible for my DPs behaviour and that his behaviour is not a reflection of me. I know in theory this is correct but I still find it difficult to actually feel this.
He is not a bad person and we have been together 20 years but I often find him socially a bit embarrassing, he talks about himself a lot and sometimes says weird things that I don't care about if it's just me and him but I cringe when others are there. He has bad table manners etc
I'm awful aren't I ??

No you aren't.
What sort of bad table manners does he have?
I couldn't have put up with that for 20 years.

Well he eats lots of stuff with his hands

Why do you feel responsible for the way he behaves?

I understand this - when you are with someone it feels like their behaviour reflects on you, either positively or negatively. If your husband does embarrassing things you are embarrassed by association.

Not much you can do other than gently point out when he does something you do not think is socially acceptable like "DH, we are in a public place, it would be nice if you used your knife and fork like a civilized person!" In a light hearted voice, but with steely eyes.

How old are you both? Assuming he is over 40, chances are he is set in his ways and no amount of eyeballing or telling him off in public is going to get him to change his behaviour. You’re not his mum, so why act like it? If he doesn’t know how to eat correctly by now at his age, he never will.

If you’ve put up with it for 20 years, why the fuss now – what’s changed?

Yup OP, what's changed? Agree with @Snuggz

In his 40s. I don't think it used to bother me as much as he was kind of charming in his eccentricity but now he just gets on my nerves, we have less money now and everything is a bit more shit.

I know exactly what you mean. Been with DH 30 years. He is no longer working and we spend lots more time together. I can NO LONGER put up with the little things that used to annoy me - they seem HUGE now. Every day I feel so angry about stuff.
I think it's the straw that broke the camel's back.