So, he's taken the WISC once and the WJ twice, is that correct? Was he close to 99.9th on the WISC enough that it seems likely that he would hit that with some remediation of his disabilities? I ask b/c there are some kids (I have one) for whom the disabilities may be something for which they can learn to compensate over time, but the scores for DYS may not be in the cards. My one who is seriously 2e did hit DYS #s on the WISC at 7 and has had many ceiling scores since that put her awfully close on later testing but we've never applied for a few reasons mainly: 1) she's not consistently there or there at the same time on ability & achievement, and 2) I don't think that DYS would be a magic bullet to solving her problems.
I guess that I see DYS more as advocacy support and social networking for kids who really need that. My oldest really needs the company of HG peers, but my 2e one tends to be drawn more toward people who share her artistic and creative interests than intellect.
I guess that what I'm getting at is two fold. How much do you need DYS and is that need so major that it is worth retesting again? Is the money and the possible stress worth it? That is something only you can know, of course.