Can an employer decrease your pay by 50%?

In law, such a reduction would represent either unfair or unlawful dismissal. While employers can change contracts, and reduce pay, any change of more than 25% amounts to a dismissal.

I assume you are salaried? and not dependent upon commision?

Of course. If its legal to raise your pay 50%, why would the decrease be illegal? Assuming that you still make at least minimum wage.

each so often, it relies upon on your employment status. I even have seen human beings lose cents simply by status transformations, extraordinarily union-contributors. I propose you talk with your enterprise in the previous making surprising judgements or conclusions.

Yes if your pay is subject to on target sales.

If that is in your terms and condions then yes he can but they can only make any change after giving you a minimum of 3 months notice.

If your contract says that and you are still being paid at least the minimum wage, yes.

Depends on your contract.