i think you should experiment also some foreplay techniques to boosts you up
I have a similar problem, i know how your partner feels, it can take me a very long time to ejaculate and i have been known to have sex for hours and can put of ejaculation far too easily. Don't be offended if you struggle to help your partner reach orgasm, just try and make him feel comfortable and try to establish what sexual techniques make him feel like he is going to ejaculate and then try to use these. It seems to work for me but don't be discouraged if it doesn't work so well, everyone works differently. Have you talked to your G.P? He may have some advice on the subject.
Take care.
He should see a dr, this could be a serious health problem.