This is just for your information. I have worked as a hoapital microbiologist for 28 years, before retiring with pd.
Indiana is not a lyme disease state, however, a doctor friend brought in a tick which was probably in the nymph stage, because it was very tiny. We identified it as the tick (usually a deer tick) that carrys the Lyme Disease organism. Although we are not in an endemic area, Lyme Disease is not diagnosed very often. I agree with you that the average physician will probably misdiagnose it.
90% of persons biten by the deer tick develop a rash around the infected area, and, if treated right away, the infection will clear up.
Left untreated, many organs can be affected, including the nervous system, but may still be teatable. The blood test does give false positives, but the fact your dad is improving on antibiotics and gave a positive Lyme test, indicates you are right on target.
When i was attending meatings, one was a real learning experience. They would present the history of the patient, and show some slides and we would diagnose the case. One thing that narrowe it down was the state the patient lived. One came from the SouthWest and was infected while cleaning a rabbit. First thought, Tuleremia. Wrond, The bacteria that causes the plague i common in that area.
The doctors who misdiagnose your dad should have ruled out Lyme Disease, because he livea in an endemic area,