To answer your questions
1) The undergraduate GPA will not matter much since you have a masters degree with a high GPA from a top school. I will discuss your potential issues with getting into a top 50 below, but the UG GPA is not the issue.
2) CFA will not matter much for PhD admissions.
3) Age is not a problem. Business School PhD programs are generally willing to take on applicants in their 30's, especially if they have some relevant work experience. Maybe a few top tier places wouldn't, but you are not aiming for those places. Quite a few people on this board started their PhD's in their 30's, myself included. A few were even over 40.
4) Canadian and US PhD programs of similar quality have similar competitiveness.
Now as to getting into top 50 programs, your issues are minimal research experience and only decent references. References matter a lot, and while a professor saying that you took a couple of classes and did well is good, but for getting into good programs you need more informative letters like from a research advisor/supervisor or a professor who has previously helped students get into good PhD programs and can directly compare your abilities to theirs.
That is not to say a top 50 admit is not possible -find out from your professors where students from your masters program have previously gotten into and how you compare to them- but it will probably be difficult. Also, how quantitative your masters degree program is could make a difference. Some MSc in Finance programs are more comparable to masters degrees in quant finance and some are more designed around training CFA's and analysts -which is what I suspect your program is. The more quantitative programs will be perceived more positively in the applications process.