The 550/300 setup with no rear bar is actually what Shaikh recommends on his suspension worksheet:

I do have an aftermarket rear bar that I can put back in and fool around with at the next autox (aug 29).

It is also lot dependent. A setup like that would be more for a SCCA style event where the car is going to be seeing faster speeds. Local lots tend to be smaller with lower speeds and more bumps making them a different ball game. Your money would have been much better spent on R-compounds and by that I mean an Auto X compound. Either a Hoosier A6 or a Kuhmo V710.

After watching your video, here is what I noticed. First off, you need to be smoother with your steering and gas inputs. Your steering inputs look abrupt and are not in synch with throttle inputs (picture a string tied from the bottom of the steering wheel to your right foot.) You shuffle your hands when you are not seeing enough lock on the steering wheel to do so. This costs time. There are times in the video when you can be more aggressive with your throttle. You need to learn how to modulate the brake pedal and
trail brake. This will allow you to drive faster into a turn, brake later and rotate the car that way. Your understeer looks mostly driver induced. However, you need to put the rear bar back in. If you think that the rear bar caused your car to crash, think again. The accident probably could have been avoided by a more experienced driver. However, thats how we learn. I totalled my AP1 S2000 by looping it into a guard rail. Did it suck? Yes. Did it give me that drive to be a better driver? Sure did. Am I a much better driver now than I was 2 years ago with the S2k? You bet your ass.

FWIW, I am now regularly competing for FTD with my 99 CSP Miata and it is not nearly modified enough to class rules in it's current state.

Here is my setup:

-Basic bolt-ons at the moment (Adaptronics and TMW ITB's going in as we speak)
-Tokico Illuminas with new FM Springs (setup works great on bumpy lots, but is a little soft for track days with high speed / high grip turns)
-RB 1 1/8th tubular bar at full stiff.
-99 Miata 12mm rear sport bar.
-1.6 Camber F and -2.0 R
-1/16 toe out F and 1/16th toe in R
-Basic weight reduction i.e. no ac, cruise, Momo wheel, Bride bucket, gutted trunk, and other misc tidbits. Car still has full interior, PS, and a hard dog bar for track days.
-225/50/14 Hoosier A6's on C-stock 14x6 Kosei wheels. Bought them with 2 auto x events on them for a measly 400.00 for wheels+tires. Although, this setup is no wheres near ideal for a CSP car, but it is enough to keep me competitive locally.

I plan on doing some auto X with my 91 Turbo Miata eventually and it is going to be setup pretty much the same as my 99.