Abby will be 10 weeks old tomorrow and weighs 1 lb 14 oz. I can't relax unless she's in her crate or I'm holding her. I'm scared to pieces that I'll lose her in some crack in the floor

I'm guessing she'll be 4 to 4.5 lbs full grown. I'm looking forward to that, while trying to enjoy this stage as well.
My boy Peanut was 4.5 lbs when he came to live with us and 5 lbs when he passed. He was the perfect size in my opinion.
Really, who wants a dog that you're afraid you'll break?