I think I can remember you posting something about your ds awhile back (I remember your name, with Iggle Piggle in it!).
First of all, you have concerns about your ds's development, your instincts are telling you something is amiss but you don't know why....so, you need to see a GP and insist on a referral to either a community paed. or a developmental paed (in fact, if you see a community paed. first, they may assess your ds and then refer you onwards to a development paed. if they are also concerned - it's up to you whether you want to cut out the middle wo/man).
Second, although your ds is giving you cause for concern, it sounds as though he has some good skills already in place (forget the tantrums, etc, for now) - the fact that he can speak is a good sign (my ds is non-verbal so has never 'proved' if he can actually talk or not) and the fact that he points to Iggle Piggle is also a good sign (my ds has never pointed).
However, some of the behaviours you have described, such as his obsessions, rigidity and lack of social skills, could indicate that he has a social communication disorder; this is why you should seek professional help to determine if this is the case or not.
Lastly, if it turns out that your ds does have a developmental disorder - or a delay - then it is not because of anything you have or have not done. I hope you get some answers soon and good luck - feel free to ask any further questions.