I wouldn’t mess with the fluid. DOT4 is more hygroscopic - will take in moisture.
The smell of slipping is concerning though. Being careful and limiting shifts is smart, but if it persists, there could be binding in the release mechanism or additional wear happening from cold-related issues.
I found a fairly base OR for about $45K out the door, but had to have it shipped in from out of state. The manual is brilliant. Much better than the Bronco.