You are being unreasonable in your response, but not your fears.
I find it ironic your user name is fedupwithjudgemebtalpeople when that's what your being 
It very easy to judge somebody else and not realise we're doing it. A judgement is an opinion, you clearly have that and have expressed that frustration rather than actually trying to help him.
If your BF does have a fear, trying to shame him or getting angry at isn't very nice. It may not be on something you can empathise with but try to think about how you feel about a fear of yours and how you'd feel if your BF showed complete irritation at it. For example many people have a fear of spiders or heights (which makes less sense than a fear of driving, given how many people are injured and die each year on the roads compared with spiders or heights). How would you feel if somebody was irritated, or belittled or ridiculed you for your fear?
If you are thinking of getting married and having kids, you could really do with learning how to see problems from your BF's point of view and working through them on that basis, rather than making a judgement and getting irritated.
First thing is to apologise for being on 'send' rather than actually asking him about his fears. Ask him why he's putting it off, ask if he's worried and exactly what it is worrying him. Then chat those fears through so he feels empowered to try to change them and put together a list of what needs doing to achieve it. He may well be happy to tick off certain aspects without worry now which will get him closer, even if he thinks he can't do it all. Eg apply for provisional, study for theory, take theory...
He may well be saying he's going to do it to get the courage up to do it. People use positive language as much to persuade themselves it's possible, as to communicate intentions to others.
A little empathy will really improve your relationship for the future.