1. Yes, they can 应聘秘书、空姐 at 40岁、50. The point is how much energy do they have? How long can they work. Those people working at 40 50 have build up everything BEFORE 40 or 50. And you just start from the scrach. So the difference will be they work for fun and you work to meet the end.
2. You can spend as much time as possible to learn English and I am sure you can master it very well in the end. BUT, how to support the family during these days? Anybody ever tried to study English for 2 years without any income for the family?