"I think he is beginning to realise that I cant actually MAKE him do anything."
Every child realises that at some point.
"What are your tips for getting your DC to co-operate."
Sod the discipline ideas. You'll still have battle and conflict on your hands.
Find things for you and your child to do which both genuinely prefer to the original rejected suggestion.
"to tidy his room"
Ask him. Is he happy with toys all over the floor? If so then fine, it's his room. Would he like you to help him tidy? Help him. Would he like the two of you to invent a tidying game? [me, I actively enjoy putting things away for members of my family, some of whom are in their 30s. Every item put in its home is a gift to the owner, who can then find it again easily. Perhaps sometimes you'd like to tidy his room as a gift to him, a gift without strings.]
"go in the bath". Don't have a bath then. What's the big deal? Go for a swim once a week, that'll get him clean. If there aren't interesting things to do in the bath at the moment, then leave bathing until it is interesting (some children like to bathe with one or other parent; some enjoy bathing at friends houses or with friends when they come to your house. Why would anyone go in a bath simply as a chore? boooo-ring!
"go to bed" I'm one of yer Alfie-Kohn-type no bedtime people. If someone isn't tired and doesn't want to go to bed, then why go to bed? I'd support them in that decision. If they don't want to go to bed because they have more fun things they want to play with, then you need to make going to bed be a really wonderful and lovely thing to do, with hugs and quiet stories with soft toys and whatever else will be more attractive than not being in bed. Having a fight about it is hardly going to make them pleasantly drowsy.
"come to the dinner table" If not hungry, then eat later. If they'd rather eat somewhere else then either have a carpet picnic with them, or provide something sufficiently interesting at the table to make it the preferred place to sit and eat.
I think we all make a lot of rods for our own backs (I know that's a favourite mumsnet phrase by having a certain adult-imposed idea about how the day ought to look. If we let go of those arbitrary rules, our family lives will look less conventional but considerably happier and less conflict-ridden.