Feel like I’m going insane 36 weeks pregnant, need advice. 😣🥲

Long story but here it goes... my husband owns an apartment building. I live in a duplex that my grandparents own. They live downstairs, I live upstairs. When I got married, my husband moved in with me here and rented out his apartment. My grandfather down stairs is a chain smoker and he smokes inside 100% of the time. (No, he won't stop.) it never bothered me the 4 years I lived here until I got pregnant and my nose got a lot more sensitive... now I smell it almost everyday. My husband and I are in the process of building a house but it won't be ready for 6 months. I'm due in less than 4 weeks... I've been going back & forth for months if we should move into my husbands apartment that he owns because 1) there won't be any smokey smell and 2) it's a much bigger space. The only thing that stopped us was that I am absolutely terrified to tell my grandparents I was moving... they would be heartbroken that l'm leaving before my house is ready and ‘taking away' their first great grandchild... so I have been sticking out here but l've been miserable. Pregnancy has not been kind to my emotions, and I have a mental breakdown hysterical crying fit at least once a week about how I don't want to live here with a baby and have her clothes smell... not to mention the possibility of SIDS from the cigarettes. Now I'm less than a month from giving birth & I have no nursery or anything set up because I’ve convinced myself we would just move... well now I ne make that decision. Like today. But I cannot get past how awful it will be to tell my grandparents. They will be so upset, and they won't understand. They're so old fashioned if I mentioned anything about the smoke bothering me they wouldn't understand. They won't understand if I tell them I'm moving because the other apartment is bigger since they raised two kids in this small space. It's been eating me alive my entire pregnancy and I feel like l've run out of time. I HAVE to make a decision. I thought I finally came to a decision the other day, just fuck it let's move. But then as soon as I got my husband on bored to pack up all our things & move at 36 weeks pregnant, I got this gut feeling I'm making a huge mistake. That it won't feel like home when I take my baby home to somewhere I barely know... that it's not worth hurting my grandparents feelings.... It's not worth the stress of packing up 5 years of things & moving when I can go into labor any minute... one thing l've learned being pregnant is I CANT trust my gut. I have painstakingly gone back & forth on this decision for 9 months! I can't take it anymore I feel like l'm going insane. I can't sleep anymore all I do is go back and forth on this decision. Please please please, give me your advice. What would you do? Stay in the place you've called home for 5 years even if it's small and has third hand smoke? Or pack up everything 3 weeks before your due date, spend a bunch of money on new furniture for the space, just to have it smell better and be a little bit bigger? Like I said, my house will be built in 6 months so idk if it's worth all the hassle to move to another apartment for such a short amount of time. HELP. 😢