Try love-bombing him. When you need the loo (not when you are bursting, when you first realise) give him a massive hug and rock him and say, 'Oh no! I need the loo and I don't want to let you go. I love you so much I don't want to leave you even to go to the loo. What can I do?'
Make a game of it. 'OK. I'll be a big girl and go to the loo.' Start to get up then change your mind and hug him again. 'Oh no! I can't! I can't bear to leave you!' Do this a couple of times, with a twinkle in your eye so he knows it's a game but also thinks you mean it.
Then get a transference object, like a teddy and say, 'I'm going to have to let teddy give you my cuddles while I wee. I am SO jealous of teddy for having my cuddles with you. But i have to, don't I?' Then say to the bear, 'Can you save some of DS's cuddles. Don't use them all up while i wee because I NEED SOME when I have finished!'
Then when you come back out of the loo, ask DS if he has any cuddles left for you or did teddy use them all up.
I promise you you won't have to do this sort of mad melodrama very often. Once or twice, if you out-hysteric him at how traumatic it is to be parted while you wee, he'll lose interest.
With making dinner, I just stuck DS in a high chair up at the counter and 'we' made dinner together. I'd give him a simple or unnecessary job like wiping the potatoes or stirring the (dry, uncooked) rice. And we'd have music on and sing along.
It's very boring, but it passes.