This is how I see it. You have been beat down and unhappy for far too long. You need to work through and get passed your years of unhappiness, and if this new woman can bring out feelings you thought you'd never feel again, and help you to regain a healthy mental state, then why not?
Since she is in a similar situation, maybe the two of you could draw strength from each other? I would discuss it with her ahead of time that
it's possible that the relationship won't pan out, and that maybe it will only be a stepping stone relationship, but you'd like to give it a try
and see where things go. If you are honest and up front with her from the beginning, that would be a good start. If the two of you can make each
other happy, even for a short time, I think it's worth it. Why sit back and watch life pass you by when you could be living it? Life is far too
short to be so unhappy and it's time you had some happiness in your life.