[cymnPrayerm]

salam, try this:

how him the miracles of the Quran and hadith. tell him about the challenge of the Quran, no human (and there have been peopel who have attempted this) has been able to think of and write a surah which can be compared to any surah in the Quran. this should be enough to convince anyone that the Quran is not/cannot be from man, it must be from god.

you said - I have tried to talk to him about the fact that if one believes in God then one should do what God asks, but he feels that Islam does not fit into the 'way he is', and although he appreciates there are good things in it, he feels that it is too restrictive for him and he would be happier without it, even thinking he would be a better person if he didn't have to constantly worry about feeling guilty for things he does which are not allowed in Islam

explain to him that when we leave sins which we enjoy doing we are only helping ourselves. wallahi we are not helping Allah nor are we doing him a favor Allah doesnt need us, when we get up 3 am for fajr we have done somethign which will bring us closer to Allah and closer to forgiveness and paradise, tell him that when we refrain from somethign haram that we enjoy we doing OURSELVES a favor. also ask him to try and think about all the good that comes from avoiding haram like for example a muslim has difficulty in staying away from alcohol but if does he
-would be left with mroe money
-he would live longer
-he would be more healthy
-better role model for his kids
-he has pleased Allah
-gotten himself closer to jannah and further away from hell