being with your in laws is enough to stress anyone out.
I saw mine once or twice a week when I was pregnant and it drove me insane.
My MIL is very overpowering and acts like SHE was mother of the earth forever, this is why my DH and BIL were and are still emotional wrecks.
I think you are showing great restraint, I wouldv'e thrown something.
Maybe you and your DH need a break together and maybe work out a set of rules regarding your MIL involvement in you, your Dh and your baby's life.
When it comes down to it, YOU are the baby's mother and knows what is best.
Good luck and keep me informed.

All the best, Catherine