If you open a company in here (also will solve legal tax issues) you can get permit for work and residency easily. Without company option I don't know about working permit. Some people around the blog will explain further.
There is a law about employment, briefly saying that; If you want to employ a foreigner, you must to prove that this job can not be handled by a Moroccan. They simply use it to avoid local unemployment. So they have a point. Since you are a Dutch, they will not consider you as a native speaker, which can be a prove to employ a native speaker as a teacher. In this issue, the celta certification will be included in game. If this certification is something rare in here, the schools can solve your issue. But maybe there are some walkarounds in some fields like language teacher. Some other people can clear up this detail also.
Flatshare is hard deal. Try to find a good mate and evaluate good. This is what I can suggest so far. And many of the offers rising until 5000 - 6000 dirhams in a flat with furniture. (take out one zero, dirham becomes approx in euro). Anyway, 5000 - 6000 dirhams is an amount which is enough for you to hire a studio alone with a furniture. Unless you got an offer less than 4000, not logic to flatshare.
Safe areas...
If you don't care too much about young guys compliments to you on streets, nearly all regions in city center can be considered as safe. Since there are so strict regulations about guns, knifes etc. in Morocco, there is no vital risk. Just young people loves to compliment : )
Your dog...
Big or small, if it barks or if it will use the building as a toilet, it will be a headache for you. If not just bring it. I know many people keeps at home. Normally (as far as I know) forbidden in mass living areas (buildings). But Moroccan's are hot blooded and friendly people. Just don't let your dog to disturb them.
Start with a home;
Here comes your links
There is no mass transportation in Casablanca except rail systems. Actually there is but... Anyway can not explain, must to be seen : )
Check for regions Anfa, 2 Mars, Bourgogne. Those are good choice for a woman and will not cause a transportation trouble. On websites, do not consider centre ville or maarif (which also must be center). Somehow even homes out of center can be tagged with this 2. Expecially the tag "maarif extension" can be some where until siberia.
I just changed home and got enough experience. Golden rules in Casablanca;
1. Never pay anything for visits. Tell them if you hire, you pay. If you pay per visit, you'll visit millions of homes which do not fit your criterias.
2. Never call or visit an anounce without a picture. There are many old buildings in Casablanca. Expecially in city center. Anounces without pictures 80% will take you to a home like refugee camp.
3. Never pay anything before signing contract. Like "pay me 500 dirhams to block the home for you, When the owner will come from (some far city) you will sign the contract" etc. etc.
4. If you call an anounce and they told you "that home is hired but if you get intrested..." Just close the phone. Cheap trick to show great homes with great prices to catch people. But somehow all hired : )
5. Comission fees; Immobiler companies 1 month hire, freelancers (called simsar in here) half month hire. But even comissioners coming with their pyjamas and slippers have companies : )
If they demand full hire, ask for their business cards and after visit their offices. Than sure pay.
Finally, before deciding to take a step for a home, I suggest to write here, give the link and ask peoples experience about the region and price. You'll have many answer.
Good luck