Hi naturebabe. I am sorry about your dad's tick bite. Please let him know the only proper way to remove the tick is with tweezers. Improper removal increases the risk of infection.
It is good you know that the tick can be tested. I suggest calling IgeneX at 800-832-3200 and see if they can test the part of the tick you have. There may be enough to test its DNA.
From what I understand, the recommended dose of Doxy for Lyme is 300-600 mg daily with 400 mg often given. I believe the recommended minimum treatment time for an infection caught within two weeks of the bite is six weeks of the proper dose antibiotic.
I hope the tick was not infected, but it is good that you know what to do.