Dear @Malcolm,
Thank you for reaching out to us again.
Yes, the (valid) passport and the residence permit will be the required documents to present at the immigration (airport). I couldn't think about any other document in that respect. Just make sure not to exceed 6 months of staying abroad in general (as Éanna explained in one of your earlier opened threads before) and don't make the impression that your actual residence/centre of life is not in Germany (I remember that your husband has a business in your country of origin, right?).
In case he is receiving money from the jobcenter, he needs to inform them. In general, job center beneficiaries are granted up to three weeks being absent per year. Otherwise it may have an impact on the payments. However, if he has a business and actually generates income, you have to declare it to the jobcenter anyway.
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,
Meike