While this is a good article explaining why the Rifampin/Doxy combo is used, it only speaks to the Rifampin dose in that combo:
www.lymebook.com/antibiotic-treatment-for-babesia-bartonella-ehrlichia-co-infections"It is best used in combination with certain other antibiotics. Frequently, those combinations include rifampin with doxycycline or rifampin with clarithromycin. The combination of rifampin with doxycycline is especially helpful when a patient with Bartonella/BLO is also infected with either Ehrlichia or Lyme. The dosage of rifampin is 300 mg per day for the first week; increase to 600 mg once a day after the first week. It is advisable to use rifampin in the evening (not at bedtime) on an empty stomach, three hours or more after a meal. It may be used in the morning an hour before breakfast also. "
I really couldn't find anything that I would trust to compare to for doses of Doxy to be on though.
When I said that 200 mgs of Doxy wasn't enough, I didn't realize that you were on a combination therapy.
If you don't feel any improvements within a couple of months, then you need to start asking more questions like, am I detoxing enough? Do I have other co-infections that could be stopping healing? Is it time to try another abx combo? and others.
Of course, this is all just my 2 cents worth, but it is based on what I've seen on forums and the articles that I have read over the years.