I would definitely remake that front end. Your spindle should be as short as possible to reduce the leverage the tire has on it when it hits a bump and wants to go backwards and up so it doesn't bend it something fierce.
You also have a huge scrub radius, which is probably a primary factor in your lack of being able to drift.
I would also remove the space and get a bolt with a shank long enough to fit through the spindle. That little bolt is going to snap, especially since it is grade 10.9, which means it is a hardened alloy, which means it won't bend. It will just snap once it meets its threshold.
Your tie rods are also pretty skimpy.
It doesn't look like your Ackerman is not set right either, nor your king pin inclination. Here is what it looks like now, and it is not good.
Obviously, I'm guessing on the right tire line, but the left tire line is no where close to the center of the rear wheels. You do have some, but not enough for the tires to turn at the correct radii. I suspect this is probably causing your bouncing as the outside tire isn't turning a big enough radius in order to be pointed into your drift, so it is being dragged along and this is causing it to bounce.
Your king pin inclination is also giving you a big scrub radius, which is probably also contributing to your poor steering and drift performance. You have almost zero inclination and with such a long spindle, this is giving you a HUGE scrub radius. Instead of your tires rotating on the spot when you turn, I bet they turn a big circle. Your king pin should point directly into the center of where your tire contacts the ground. Yellow is the angle you have now, and the red is what it should look like.
My recomendations:
You must remake your spindles. You need to figure out the correct angle to have your king pin at. You need to run a string from your king pin back to the midpoint between your rear wheels. Where your tie rods meet the steering arm bit of the spindle is along that line. You can have it in front of it, but instead of the arm pointing in like it would if it were behind the tire, it will be pointing out.
Your spindle needs to stick out as little as possible and be as thick as possible. Your king pin needs to be as thick as possible as well. Your tie rods should also be stronger. If you hit a bump wrong at speed, you are going to have a very very bad day.
If you give me the inside diameter of the bearing on the tire, the width of the tire, the diameter of the tire, and the distance that the bearing is offset from edge of the tire on the inside, as well as the distance between the centers of your rear tires and the distance from the center of rear tire to the center of the front tire, I could make you a drawing of what I think your spindle should be.
