Moesharitza-
Let me tell you how some families I know of PRO 1 2 category racers handle it and then maybe suggest some limited involvement on your part.
I belong to a club that has a racing team component that allows me to see how the families of the racers involved deal with it all. What I have observed is that they are involved in the sport on some level. If they are not helping with the organization of the ride they are involved in the process or carrying out of the ride by helping with transportation, support with beverages and equipment or support as a sag wagon (the car that follows the people involved in the ride to help them when the need presents itself).
One of the wives and son actually ride with the club. The son races and is now state and nationally ranked. So they have taken their involvement to another level. The wife rides hard enough to keep me a cat 5 master breathing hard just to keep up with her at the front of the pack.
Levi Leipheimer's (another PRO) girlfriend, is even more proactive, I believe. She is involved in a lot of Levi's training rides by pacing him with a motor-scooter (Lambretta type motor-scooter). She is able to raise the level of training by helping him sustain intense efforts for long periods of time (like you said up to 4 hours) by helping him go faster than he would be able to go riding solo. Plus, he's not riding solo he's riding with his girlfriend.
They get to spend more time together. No it's not quality cuddly time, but it is time in the bank and a time where if you were involved like some of these folks are concerned would help alleviate all the anxiety you're feeling.
I'm only a cat 5 and put in anywhere from 4 to 5 thousand miles a year. Your PRO boyfriend is probably putting somewhere at 10 thousand miles on his bike. I've been hit by cars, had stuff thrown at me and crashed going 34 miles an hour and it's not a pretty sight. But I would venture to say that your boyfriend is one of the safest riders out there. Yeah he's a ferrocious rider, but then that is the mindset of a racer.
So again, I suggest some level of involvement on your part. No you don't have to make it your life like he does, but I believe the time investment and you being close to the situation will help relieve your anxiety for what he goes through to maintain his high level of personal training. Good luck with your deicison!