"Share to Media Browser" has always retained all my chapter markers. But my maximum number would probably not exceed 20. Certainly, I've never got anywhere near 52. Possibly, there is a limit and you have exceeded the limit.
I find that "Share to Media Browser" produces better quality DVDs than when using "Share to iDVD". This does seem a little incongruous considering that the Media Browser option produces an H.264 movie, whereas the Share to iDVD route gives you an AIC movie - the same format that iMovie '09 uses for its full frame editing.
So, I would be inclined to go with the "Share to Media Browser" export and look at reducing the number of chapters, if practicable. The difficulty for you, of course, is "what's the limit" (if there is in fact a limit). Maybe someone else can offer some insight here.
John