Hi there, first off, take a deep breath because you will not only survive this, but-and I know you can't see it now-be happier in a little while.
As far as the "Internet Woman" of course he is developing feelings for her.SHE is saying all the right things, has nothing truly invested in him like you do, and sure as hell doesn't know and have lived with all his bad habits.
She is also 1,000 miles away, so, she is "safe". Take for instance they met IRL, spent a week or 2 together. Do you not think he wouldn't be comparing her to you (even subconsciously)? He would start to realize that Ms. Website is, here it comes... OMG, she's Human too!!! And has faults that irritate him! And, though she was perfectly accommodating on the computer, she actually Expects things of him?? WTH??
It's not her or you, it's the secrecy that is exciting. Once that's out of the way and he sees she is just like every one of us, she won't be that great of a Secret crush anymore.
You are not alone. We are here walking right beside you.