1995 Mazda MX-3, good body condition, only 57,600 miles. Frame rusted, getting dangerous to drive. Is it worth getting the frame repaired?

Hello, that's a question that you'll have to have addressed at a local body or fame shop near you. The cost of a reliable repair must be weight against the potential of future issues for areas not addressed. Corrosion and rust is a serious thing because it can be present where you don't see it - and safety may be compromised. Depending on the severity of the corrosion, you may be best to think of another vehicle. However, a hands on - eyes on evaluation is needed.