OP, I can well imagine your annoyance.
Kindly meant but you need to take back control.
No gaming at ALL during your working day.
I have a 19 and 23 year old so I know the noise. One has a pitch that the dogs three roads over can hear🙄.
No way would I tolerate that during the working day.
Secondly tell your husband HE is responsible for all shopping and cooking while they are here.
Leave the mess but tell your husband the minute he comes in the door to get on it.
No way would I be picking up after my sons leaving their mess about.
As for the jobs?
Yes they have summer jobs at university.
They are on sun holidays at the moment but do work for most of the summer, like their friends.
They actually like earning their own money and as someone who always had part time jobs, we actively encouraged them.
Your daughter sounds like a great young women, you have every reason to be proud of her.
Summer work and part time jobs are the making of young people.
Nothing like seeing how hard some people work for shit money to give them a taste of the real world and increase their motivation to do well at university.
Part time work, particularly those jobs that are dealing with the public are massively confidence building, adding skills that will stay with you.
Regarding the mess they leave around, my friend used to gather anything left lying about into black bags and throw them into the garage.
She said they weren't long getting the message to keep their stuff in their rooms!