I have to say that his critiques are sound. He gave me some insight on a script a few years ago and I was pleased.
I wouldn't call him a scammer because he hasn't had credits since 93. (I believe he's retired from the biz and this side job is his pension plan). If McKee was giving critiques for a couple of hundred bucks, would you call him a scammer? His credits are even thinner than Kellem's.
The fact is, anyone who offers you critiques for money, or free, should only mean one thing for you. Do you lack the experience or objectivity to self evaluate your work? Can this person's advice make your work better?
If you expect for some magical reason that this person's review of your work will make it an easier sell, then you should never pay anyone because that dream will never happen. That is not the point of having a script consultant.
If all you want is advice to possibly make your work better and you can afford it and you don't have better (free) resources, then I would appreciate the advice from anyone who can offer advice based on any industry experience.
On the other end, I should play devil's advocate and say that Kellem may be too long away from the industry to give advise based on today's standards, but I don't know if that is the case or not. He could still be keeping up.
Basically ask yourself why do you want your script read by anyone like Kellem?