He will need a lot of training.
While you are at it, you can have a think about how you are going to train your son too. My 14 year old ds cooked lasagne for us this evening. He always cleans his own room, can use the washing machine and iron. He has been making his own packed lunch since the age of 7.
He would be able to look after himself much better than your dh OP. You are making light of it now, 'bless him' etc., but remind yourself of what you wrote in your OP>
I am constantly nagging my DH about what he is not doing.
Not helping the mood at home.
I feel like I do everything.
I have always been the one to do all of the chores.
^...it's all too much for me alone
It makes me feel like he doesn't respect me...
I have asked him to help me but I get lots of excuses.
I work two days.
My parents watch DS so DH has no responsibilities there.
I make his dinner and lunch even when I am at work.
I do all the washing, ironing, cleaning, shopping, tidying... everything.
Quite strong statements and you do sound unhappy and overburdened when there is absolutely no need for it at all. There are two adults in the house. Why don't you treat him like one and let him develop the skills he is lacking?
You would both be much happier and a better role model for your son.