You're assembling the stem in the wrong order.
Place the spacers and the stem loosely on the steerer. Make sure there the steerer ends about 3mm below the stem or top spacer (whichever is on top ) so the top cap pushes on the stem/spacers and not the steerer.
Use the bolt through the top cap and the star nut to set the headset preload ( so there's no play in the headset but it turns smoothly ). Tighten stem bolts to retain steerer. As for the bars in the stem, its normal to have a small gap between the plate and the stem. Check that your bar clamp diameter is the same as the stem.