Hi Maddy,
I agree with what most have said here ... that you absolutely can't have a romantic relationship unless there is some level of physical attraction. Like someone suggested earlier, if you are repulsed at the thought of kissing him, romantic love just won't happen. A cruel joke of nature perhaps, but true.
I would like to add something ... consider the effect on Chris of a rejection when you first meet in person. Believe me, he will know it within minutes of meeting you. Because you already have a strong emotional attraction for each other, and assuming that he will be physically attracted to you when you meet, his romantic feelings toward you will become immeasurably stronger after that first meeting, and he will be much more hurt than he would if you were to break it off now and never meet.
It isn't shallow to need some chemistry to spark a romance, but it would be incredibly selfish of you to meet him in person anyway, virtually knowing that a romantic relationship with him will be impossible for you. I don't mean to sound critical or preachy, Maddy, but it occurs to me that Chris has a MUCH bigger problem than you do. People here are trying to help you, which is very sweet ... but you shouldn't forget that there are two people affected by this.
My advice is that you should break off the friendship now, so he can start to deal with the pain of your rejection immediately. Unfortunately, you will be losing a good friend, but you certainly don't want him to be hanging on to a false hope for months or even years because you are still in his life.
Good luck,
Zack.
ps To avoid this kind of disaster in the future ... when you meet someone online, and it looks like there may be an emotional spark, you should meet him (in a public place) at a much earlier point (pictures just don't do it). It will save you both a lot of potential pain.