MAC has a great return policy. just keep the box and return it if you don’t their stuff. so try to do that. i have saved a ton of money returning anything i don’t like.
have you tried studio sculpt foundation? i use NC 42 which might be lighter than studio fix’s NC 42, so try few shades in studio sculp. it seriously gives such a nice look to my face without drying. i have horribly dry skin.
Also if the prolong wear foundation is drying you out, and turning dark later it means it is oxidizing on you, so you should definitly return it.