I think it's up to you to negociate the terms of your contract, i.e. no "unofficial" work. As for accepting or not the job, it depends if you have some perspectives for the next weeks or not, in terms of getting another job. I think 3-4 hours a day is not too much, and it could be interesting. After all, you can work without stressing yourself, and you might learn a thing or two. It won't necessarily improve your CV, but it can have an impact on yourself. After all, coming out of a bad experience, it could be an opportunity to show yourself that you can "do it right".

So yup, flex your muscles, negotiate your terms, and get the most out of it.