David - in reviewing your soil test results, I see that your soil is generally healthy with the exception of low Potassium.  Magnesium is essential for Nitrogen uptake and chlorophyll synthesis and is quite mobile in plants. 
Soil nutrient interactions are quite complex and your concern about trying to lower the Magnesium is warranted.   Unless your lawn is not showing green growth, I would recommend that you utilize the recommendations and apply Nitrogen and Potassium which will over time affect the Magnesium and Calcium levels.  You may even apply a separate Potassium fertilizer to address the Below Optimum level of that nutrient.  For any product, you can come back to the MSU soil test results site and enter the numbers from the bag  into the Fertilizer Calculator (found under Tools).  The site will calculate how much of that product to apply in one year over 1,000 sq. ft.  Remember to pro-rate the amount if your area is more or less than 1,000 sq. ft.

As for the Phosphorous, it readily binds with the soil and is very challenging to lower.  Much of Michigan soils have high Phosphorous levels since homeowners have consistently applied Phosphorous when not needed.  Make sure the middle number on your fertilizer is 0 so you don't apply any more which clearly is not needed.  Instead, focus on the health of your soil and maintain the organic matter with grass clippings and mulched leaves.  Apply Nitrogen and Potassium fertilizers as recommended.

Hope that helps and good job starting with a soil test to know the health of your soil!