First of all, you seem like a great mother, that you really care for his best.
I am an FFB but was OTD for some of my teenage years and up until a few months ago. It took a long time for me and my parents to come to terms with each other, but now we have a tremendous relationship and I love and respect my parents immensely.
What frustrated me most about the system and caused me to lose interest were:
1) From how I saw the system, there were so many inconsistencies in the way my teachers and parents acted and the way they expected me to act.
2) As much as they (my parents and school) would say that they don’t expect everyone to follow a one-size-fits-all level of Judaism, everyone who does not follow their level of observance is radically in need of help (i.e. read the Dvar Torah from a Chayal blog)
3) My parents and the school cared more for how others viewed them than about the individual child.
IMHO a child first needs to learn responsibility before he can appreciate the Torah and Mitzvos. His role models need to exemplify integrity and responsibility. He doesn’t need to see that Judaism is ‘also’ fun; he needs to see how awesome Judaism actually is!
About the computer, it seems more like he is testing you. Have him earn the money to buy it himself; it may encourage him to get a job.
Sing your heart out all to the zmiros by the Shabbos meal! Bring up all your kosher experiences which could only happen in a Jewish framework (like something that had to have happened on Shabbos or Chag), and don’t make it appear like your trying to prove a point.
Let your children see how much you love the mitzvos. It doesn’t need to be said, all they need to see is that preparing for Shabbos and waking up for minyan, truly makes you happy.
Encouraging him to be productive is the first step toward building up his self-esteem. Give him space (but don’t be an enabler) while allowing him see that every single mitzva makes sense, and he’ll come back on his own.
Be strong in your values for yourself so he sees Torah is true! If he and the rest of the children see that Judiasm is not only worth living, but that you truly are obsessed with it, be”H you should see nachas.