When I rode BMX fifteen years ago, I really liked the ACS Claws freewheels. They were good quality and not overpriced. I think they're still in production.
It freezing up in cold weather is probably a result of the kind of oil that's on the pawls. If you disassemble your Dicta, degrease it, and put it back together with appropriate light oil on the pawls, it'll probably work just fine after that.