I would talk to the landlord first. Just explain what’s happened. If he’s reasonable, he will refund in full. Because your case is beyond your control and your family must go outside U.S. by law, i think the landlord will accept cancellation. Per my understanding, 1st month rent and Move in/out fee should be anyhow refunded to you because the leasing period is not started yet. Also, the security deposit is to cover landlord’s economic loss in case the tenants damage the property during their tenancy. If still the landlord wants to keep some of the deposit, i think he should prove the loss he would suffer from this cancellation, which I don’t see because you just signed it today. So, just call and explain.