Getting PhD opportunities abroad in my thirties
It is not easy to answer your question, since it is not clear what is your goal (e.g. what you mean by a "good" school), and what is your current situation (e.g. research expertise and area). 

If by a "good" school you mean a University in US or Western Europe, then you probably know that there is a really strong competition there. You should carefully evaluate your personal strengths and play on them if you want to be admitted. Your current age will not be seen as disadvantage (but perhaps will not be seen as advantage either). However, you slow progress through your degrees may raise questions. Your potential supervisors want to choose a candidate who is likely to complete the project in time. You had to spend a lot of time doing TA's in your country, which slowed your progress - how can you ensure this will not happen with your PhD program?

Another important factor is your research field and research expertise. You don't have published papers, which is usually a disadvantage for PhD admissions. You will have to provide a sample of your academic writing - do you already have it? What about your research area (educational background) - is it modern and currently developing with a huge demand for specialists, or is it classical, well-established, and producing a lot of unemployed PhD's every year?

Lastly, your consider jumping a ship in a middle of your PhD program. How do you think you current School will like it? They invested resources in someone, who took them and left them for a better place. If the only reason for doing this is your personal comfort, then the decision you consider is (in my opinion) very non-ethical. I would not personally consider hiring someone as a PhD candidate if I am not sure they are committed to work to completion. Please, realise that our resources (time and money) in academia are extremely tight - don't waste them for your own joy.