The numbers you supplied the calculator are raw numbers with the spin expression not entered into it for a proper equation to meet your need.
From this rookie's perspective:
Just like a wind direction but no wind strength to help you correct your course. Your spin is your primary issue at a loss of 3 tenths? You need to stable out your launch and get in a few clean runs with very little spin. Your MPH will be lower at first but your times will be quicker until you cross the threshold where torque overcomes traction and you are forced to back off. This was a problem when you were stock, in first gear, now with the additions to the rear wheels it has traversed into second gear and causes you even more time loss as you fight the machine to regain your timing.
Test and tune, you need to just use the track time to get first gear right and try to run the second gear, get off the gas and and cruise down the track and pick up your slip. Once you get the first two gears right with good shifts and limited spin and very little wheel hop you will be able to hit third with confidence and get to see your improvements in your skills. Do you heel-toe the clutch and brake? Do you know the feel of a wheel hop spin vs a over throttle launch? Are you able to load your drivetrain and take up the slack so at launch you don't snap your tires free from just the slack being absorbed? Getting the feel after making changes just slight enough for your car to become a different car seems to sound like BS but it can make you start all over again. Street tires for racing suck, it is not their intended purpose and applying the right tires even for a test might show you what a real launch should be and how those stocks are now your new problem along with shifting a manual with your hand on the far side of the shifter or your hand turning on the top and makes you pull it toward you instead of straight back or over up and past 3rd.
Unless there is something wrong with your car mechanically the problem is?