ATP-CTP
Couple of issues with your plan!
1. You cannot sit the written exams until you complete the FAA ATP-CTP course from an approved provider such as CAE Dallas
2. The written exams must be sat in the US at an approved(CATS or Laser test location.
If you want to complete this in the least painful way study the FAA written exams and then complete the ATP-CTP and sit the exam a day or so after the ATP-CTP.
Once completed you have 5 years to complete the ATP check ride