Hi Puffyfish,
Try to always remember, what's important is your hubby's support and undertstanding. It seems your hubby is one. No point getting affected by your FIL. There obviously a misundertanding. Maybe your FIL worried that you will kick him out of the flat to make space for baby... Anyway, just remember, no point getting stressed over things that you can't have control over. Be positive and cheer up for baby. Moreover, things might get worse after the baby is borne....