I don't understand whether you have successfully driven onto the highway or your car has broken down on the sliproad (BrE). The first 3 say that you are either close to or just past exit 4, but number 4 says you tried to get onto the highway using mileposter 4, but the car died.
As a BrE speaker, my terminology is different, but when I call a breakdown firm, I have to say:
Hi, my name is XXXXX. My membership number is XXXXXX. My car has broken down. I am on the M25 (that is the name of a motorway), about a mile past Junction 12. Please come as quickly as possible.
My car has broken down on the A27 about halfway between Falmer and Lewes.
My car has broken down on Edburton Avenue, near the corner of Ditchling Rise.





