Hi OP,
My DS sounds very similar to yours.
He was born by ventouse in 2004.
He has dyspraxia, glue ear, very poor eyesight and spinal problems. When he was a tiny baby he screamed for HOURS which I now think was due to pain in his neck/back.
Yes, I think the ventouse has contributed to his problems.
He's also funny, sensitive and very clever. He never crawled, but he stood up and walked (holding on to the furniture) at 8 months old. He couldn't read until he was 7 years old, and has only properly got the hang of it in the last year (he's almost 10 now). He can't use cutlery and his fine motor skills are poor.
However: without the ventouse, he might not have survived and I would have been even more mangled internally due to the type of c-section I'd have needed! There wasn't time for any warnings; he just needed to be born NOW, and ventouse was quicker than c-section.
Both his OTs and his ENT consultant believe that special needs are more likely to arise when there has been an assisted birth (ventouse, forceps or c-section), based on the children they've seen over the years, and it's something that fascinates me. I know many children with SN and not a single one of them had a "normal" (I.e. Vaginal, with no instruments) birth. I would love to see some research being done on this.
Of course, I also know plenty of children who had traumatic births who DON'T have SN! I'm not against assisted births. As I said, without the intervention, my DS would probably be dead. I think this should be talked about more though. I've often wanted to start a thread on MN about this!