Hey Onepixel. IGenex is an excellent test for Lyme but not so much for co-infections (I know you don't want to hear that). The best test for Bart would be the FISH test which detects the RNA of the bacteria in the blood.
The problem is that it still has a high false negative rate so if it comes back negative you may not want to treat but if you're having typical Bart symptoms that's what you should really go by. There was a study done on ticks in NJ that revealed that Bart was even more prevalent than Lyme.
The actual drawing of the blood should be covered if they're in network or accept your insurance. Only the IGenex test is what you would have to pay out of pocket for.
Your B12 levels are low so you should be taking the methylcobalamin form which is the active form of B12 meaning your body doesn't have to convert the cyanocobalamin to the methyl form thus enhancing absorption because it's already in the bioavailable form.
You may see a difference in energy levels from taking the B12 if your energy is low. I also recommend taking 2000 I.U. of Vitamin D3 and more if you're deficient and a good magnesium supplement as Lyme eats it up possibly causing a deficiency.