I would like address several of your concerns and clarify several points raised by other posters.
1. How high do you need score on the LSAT test to be accepted by an ABA-approved law school?
With your experiences, you are a very good diversifying factor to any law school. I would guess if you can score 150+, you will have a good chance to be admitted by a 3rd-tier law school. With a good personal statement, you might be admitted by some top schools too.
2. How hard is law school?
Not hard at all. But it is tedious and time-consuming. Nowadays it is very rare for an admitted students to drop out because of pure grades. Most dropped out because of non-academic reasons.
3. Job prospects?
With your age, it is very hard to get a big law job, which means you are not likely to get 100K+ salary. The truth is that even for some Chinese JDs in their 20s big law jobs are hard to get unless they are in the top of their class. Many JDs directly go back to China, either by necessity or by choice.
If you are open to go back to China to teach or to practice after graduation, job prospects are bright at this time.
4. Don't worry about your age.
It is not that unusual to see some JDs in their 40s, especially in some part-time programs.
If this is what you really want to do, and the urge is so strong, I would suggest that you do it. No matter what you do, you would be 3 or 4 years older in 3 or 4 years.
We human beings tend to regret more for something we did not do than we did.
5. Some pratical suggestions.
Take the LSAT first and apply. After submitting your applications, sit in some law school classes and get a feel of what law school is about.
Visit http://www.totoolaw.com. That is a site for Chinese JDs/LLM students.
It is your life and you are the best person to decide what to do. Don't be swayed by others' opinion.
You can always quit once you are in !