Approaching a professor for a postdoc, after not taking his previous postdoc offer in favor of an industry job
Start the conversation by being honest: describe what had happened, and assure them that it's only because of personal reasons that you could not accept their offer, not just the industry offer. You did the right thing by emailing them in March to keep them in the loop. However, I would emphasize that the reason that you didn't email them sooner was because of the personal stuff.

The same reasoning goes for your 1 year gap: if you do amazing work in your postdoc all will be forgiven. You need to convince the advisor that they can trust you to do well despite the initial setback (which was not something you could control), and the only way I can think of doing this is by telling them the truth. 

I had a collaborator (not a postdoc) who left academia for personal reasons and returned to work with me (their story is somewhat similar to what you're describing, though the personal circumstances are different). I was very happy with them and was understanding regarding their situation. I'd like to think that I'm not an exception: most reasonable people understand that their students/postdocs have a life outside academia, and this particular advisor sounds like they should be as well. 

Your age is not a major factor in this equation. I'd say that 27 is relatively young (I started my PhD at the ripe old age of 28).