I grew up in a split entry home in a suburb of Minneapolis and we weathered many very severe storms in our basement. We began sheltering exactly where it's been determined to be one of the most UN-safe locations; the SW corner. Upon witnessing first hand what happens in that segment of the home (windward side) after the Tornado Outbreak on May 6, 1965, we sheltered under the stairs ever afterward. Too many basements, whether full or partial had blocks tumbled into the SW corner and many people lost their lives in that corner of their homes. One image that sticks firmly in my mind to this day is the stairwells that stood up through the floors. Nothing else left - just the stairwells.
Our basement was unfinished, yet the stairs were sturdy and we would tuck well under where they met the basement floor.
It's been determined that the best bet is to shelter somewhere in the Leeward side (usually the E/NE portion) where debris is generally brought OVER and AWAY. So...I'd say to shelter under the stairs, inside that closet, since it sounds like your entry is on the Eastern side of the home.
Also, I'll link FEMA's specs on building your own storm/safe room. Info there you can download for building plans:
And, Tx Tech's recommendations per the same:
Please take the time to read them and share them with your husband. You're doing the best thing possible - being aware and pro-active regarding the safety of your family in your home.