My first thought was "what's a bridge camera!", then i googled it and had a "ah ha" moment..I actually considered it to be some kind of camera that had some kind of bridge fixed to it
My camera is an rather old Pentax optio S60 and like the Nikon P90 you borrowed has a limited field of focus on macro.
You can see in your first picture that the chela is kinda focused while the mesasoma is blurred. Your other pictures that you have taken with the subject positioned side on are better focused because here the field of focus enables the subject to remain within the field of focus.
You can look through the post "My collection" in "Scorpion Pictures/Videos" to get a idea of the quality of my camera's macro picture potential.
I also use a tripod on macro with the timer enabled to eliminate camera shake when i take a picture although that's no guarantee that the picture will be perfect...Still, the good thing with digitals is that if your first try was unsuccessful you can always delete it and try again.
Lighting is a very important part of getting a good picture and nothing beats natural sunlight although i'm now starting to experiment with putting a piece of bubble wrap or something similar over the flash housing to cut down the ugly stark glare of the flash...I've yet to find the perfect solution but i'm confident i will
