Katt, I'd say go for it. Just so long as you take proper precautions when you meet initially & get him to introduce you to friends & family etc it should be fine. Biological age is not an issue, so long as you are comfortable with each other.
As for explaining to people how you met - just tell them. Many thousands of people have fallen in love over the internet, but before it existed, there were always penpals, dating services & all the rest. That you love each other & are good for each other that is all that matters.

Good luck & be careful.

XXX

P.S. Am pretty sure I know who it is, but I promise on pain of death not to say anything unless you ask me to.