Antidoting 200c effects with 6x?

That isn't the law of similars (homoeopathy), that is the law of same (isopathy). According to homoeopathic law, and to the experience of homoeopaths, a similar remedy must be found to antidote/counter any ill effects. In other words to cure you must do exactly as you would do in any other situation - take the symptoms, and prescribe accordingly.

There are no shortcuts in homoeopathy.

I have to ask though, if you were in perfect health prior to taking the remedy, WHY did you take it?

Oh and the other issue here, is that a remedy cannot be still in effect 4 years later. That is impossible. Our medicines are short acting - a few hours, days, possibly weeks in rare cases.

Anything happening now is a direct result of your own vital energy being out of balance, and as such a remedy applied to your individual state must be applied to get cure. Baryta carb is irrelevant at this stage.

Isopathy doesn't use the symptoms, which makes it the opposite of homoeopathy. Homoeopathy does use the symptoms must use them in fact - and as far as we know it is the only way to genuinely cure. Without symptoms we have no way of knowing if the remedy can or will cure you. Isopathy is a guess only. Isopathy rarely cures anyone. I say rarely because in fact it can be very useful in some cases ie. using a medicine made from the drug that damaged a person's organs or nosodes made from specific diseases that dramatically altered a person's health.

If you have Baryta carb symptoms now, then of course it could cure you. But the symptoms must direct us to the remedy. Even if you were 'poisoned' with Bartya-carb earlier in your life, the shape your disease takes is not determined by that remedy, but by your own internal disease pattern (miasm). In fact, chronic disease is an interplay of this internal force and any external influences, but it creates something unique and unexpected.

Antidotes for Baryta carb (should you be actually needing that) are always other remedies - Borax, Lycopodium, Anacardium etc.

The first response to a curative remedy should be aggravation, not amelioration. I would be suspicious of any medicine that starts by making a person feel good - it actually should make you feel bad first. However, one can only wait and see what happens now.

My professional advice is to NEVER experiment using our medicines. The effects can be dangerous and permanent. Stop self-prescribing, it will only end in further suffering.