@Lucinda69
Long-term hosting in a shared home situation can be quite different compared to short-term hosting because people will be "living" there, not just visiting. In my experience, long-terms stays in a shared home require a completely different set of rules, and knowing the purpose of the stay is really important. You've already gotten some really great suggestions from other hosts.
Changing your listing description or rules during a stay won't help - rules need to be agreed on BEFORE the stay, so my suggestion is to work on a draft but don't change your description or add any new rules till your current guests leave. And you need to make sure whatever rules you set, YOU need to stick to them.
Maybe in the future, think about NOT hosting longer stays. There are pros and cons and you may need to adjust your own expectations as well. If you don't want to do the home-sharing, roommate situation then IMO, you definitely should not have people staying longer than 2~3 weeks max.
But in the here and now, if they are acting in a way that bothers you, then I think it doesn't hurt to bring it up with the guests in a casual, friendly way - like any home sharing situation.
Frequent laundry (I've had the same problem before) - my suggestion is to bring this up casually with the guests. You noticed they do small frequent loads everyday and you'd much prefer if they could try to do larger loads, every 3 or 4 days. If they are taking up too much space in the fridge, mention you usually only give guests 1 shelf and while you understand 1 shelf may not always be enough, you'd appreciate if they could limit themselves to no more than 2 shelves at the most. For shared spaces, you could say you understand working from home and needing the space to work occasionally or during the day, but the purpose of the shared dining room is not to provide guests with a home office and you would like to use that space too, so you'd like them to limit use of the dining room as a work space to certain times, and you'd like privacy to cook and eat during certain times in your kitchen without feeling like you are intruding or bothering them. As you talk about these things, ask them what THEY think and what they are willing to do, be open to suggestion. I think you could also add that it's your 1st time hosting guests from more than 1~2 weeks or people working from home so you did not think to talk about these things in advance and leave it at that. No need to apologize but rather show you want to find a way for everyone (host AND guests) to enjoy the stay.
Take notes of the chat, summarize what was agreed on, thank them for understanding, then send a brief recap and thank you thru the Airbnb messenger as a follow up.
I'd image that most reasonable people will be open to an honest conversation, and understand that home-sharing requires some level of adjustment for everyone involved.
Good luck~