Ok, so I have a few little bits to add...
First and foremost DO NOT run a racing harness without roll over protection. If you are planning on getting a BRIDE Cuga, that will work fine with the stock belts until you get a roll cage. If you roll your car and the roof caves in, the stock belts allow your body to twist and move to take the force of the roof coming down on you. Harnesses do the opposite, and all of that force will be taken on by your neck, which can't handle much.
Second, your weight balance issues comes partly from you removing 100 lbs. of weight. Most of this weight came from the rear, making it an uneven weight distribution from the start. Also, without alignment adjustments, your rear tires were probably a little on the positive camber side because of the higher ride height due to the weight reduction. This problem amplifies itself under braking when even more weight is transferred off the rear onto the front. When you switch to the Odyssey PC680 I suggest buying a battery relocation kit along with it and moving the battery to the rear of the car.
Toyo R888s are an excellent tire, but the sizes you listed are WAY too staggered for a front engine car. Since you are coming from a Porsche I will forgive you
. If you are going 305 in the rear, I would go 285 up front.
Also, feel free to PM me if you want to get more in depth about all of this or if you need price quotes on parts.