If the job pays that poorly and the benefits are that lame, go elsewhere. If your skill set makes it the only job you are qualified for, get new skills. 25 years and no retirement benefits. Sounds like a lot of non-union workers who must save for their own retirement directly. And certainly it was no surprise right? 25 years is a long time to be waiting patiently for that fully funded 401k to appear.
And that 3 credit hours amounts to teaching on the order of 30 classes, usually less due to holidays, breaks and exams. At $3500 per class taught, that works out to be $117/hour. Granted, some more hours to grade HW and exams. Even at 1/3, $39/hour is pretty good pay and a lot of people would take it. And most of these classes do not change significantly semester to semester so once a teaching plan is in place variations are going to be incremental.
Note too that one can also try to only teach classes at night thus keeping a day job full or part time. That is pretty common with city based colleges where faculty are often employed professionally.