2006 Mazda 3i rough idle and bouncing RPM?

My car would normally idle at around 750 RPM, but now idles at around 650, then drops to 500-550, shudders, then comes back up to 650, rinse, repeat. Sometimes my car will also idle at 1000 RPM. Recently, the RPM has started bouncing while I'm slowing down to a stop sometimes. It'll go too 1000, jump to... show more My car would normally idle at around 750 RPM, but now idles at around 650, then drops to 500-550, shudders, then comes back up to 650, rinse, repeat. Sometimes my car will also idle at 1000 RPM. Recently, the RPM has started bouncing while I'm slowing down to a stop sometimes. It'll go too 1000, jump to 1500, back down to 1000, back up to 1500, etc. While it does that, I can very audibly hear the car rev, and it jerks forwards, and the brakes seem to not work well at all. To avoid rear ending the person in front of me, I have to throw my car in neutral to stop. When putting it in neutral when the car does this, the RPM spikes to 3000, still bouncing, which puts it to 3500, back to 3000, etc. The only way to stop that from what I have seen is to restart the car, then that doesn't happen anymore, but I still get the low idle. I've cleaned the TB and MAF sensor, done the idle relearn procedure and ran fuel injector cleaner. I also don't see any cracks or holes in any tubes, so I doubt it's a vacuum leak. Any ideas what it might be?
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