Oh dear. I'm not surprised the SENCO wasn't much cop, good ones seem to be very few and far between. Our school doesn't even have one at the moment. 
Just about everyone I've come across who has a child with special needs, particularly ASD, has been told their child won't get a statement so its not worth applying. Standard schpiel (sp?) I'm afraid. We have been told this by the old SENCO and the Head and been spun the old 'he needs to be X number of years behind his peer group academically to get a statement and your ds is academically advanced' line. They are just trying to put you off.
Talk it through with your GP and get your ds in to see someone who knows what they're talking about. SENCOs are 'Special Educational Needs Coordinators' they simply don't have the training to make decisions about whether or not a child has a certain condition or syndrome, let alone whether or not they will get a diagnosis or statement and its not their job anyway. They are there to coordinate the help and support that children on their school's SEN Register are getting.
Twelve months ago I was where you are now, doubting myself and being told I was making a fuss about nothing. If it wasn't for this board I would probably have chickened out and that would have had dire consequences for my ds. I am not the type of person to push myself forward or rock the boat, but I came to the conclusion that I had to change that for the sake of ds1. I have since been told by several professionals that ds is likely to get a dx of ASD possibly with a comorbid dx of Dyspraxia, he has also been given an preliminary dx of Aspergers by the Paed. Just last week we met with the Ed Psych for the first time and she said there is little doubt in her mind about ds having ASD. My ds is very similar to yours.
We have only seen or spoken to any of those people because I made it happen. I went the GP in the first instance, rather than the school. I figured if they'd been so useless as to deny he had a problem for four years, they were unlikely to be much help. It was me that brought in the Ed Psych as well, I called the centre where he is due to be assessed and said both we and he couldn't cope and could they suggest anyone we could contact for support while we waited for his assessment. They were disgusted that the inclusion team weren't aware of him and told me to call them myself. They also told me call the Ed Psych crisis line and explain the situation. The duty Ed Psych called me back the next day and talked to me for over an hour, then took ds's case to their weekly meeting and they took his case up from there.
I spoke to the Inclusion team, who were not at all impressed that the school hadn't mentioned him, as they are at the school every week anyway and it wouldn't exactly have been hard for them to at least put him on their radar so-to-speak. They told me to get a GP referral for him instead as the school was obviously being obstructive.
Finally they told me to call CAMHS for further advice and get a GP referral for them as well. I did both and they have since put us in touch with a local ASD support group that we weren't aware of.
I also got him an Occupational Therapy referral regarding his dyspraxic type problems.
My ds is finally getting some support in school and they have been making an effort since all the other professionals have become involved, although things are still far from perfect.
Its well worth pushing it yourself, I honestly wish I had done it so much sooner.