i have met several men who have been like this, its not as rare as you might think.........
for what its worth i would say
1) he might be involved with someone else.........either in the real world...........or in his mind and doesnt think he is being unfaithful unless he has full sex.
2) he has issues that stop him being able to ejaculate...........you dont say whether he can climax without penetration in your presence ??
3) he has something he doesnt want you to catch.................. have you ever suggested using condoms ??
4) it hurts
the only way you will find out is to ask him and deal with his responses sympathetically
re : cybersex......................... i wonder if you like the detachment that this sort of sex creates..............?? bit of a pattern here for you !!!
good luck