Hey,
Sounds like your account is getting logged out from inactivity. The script is designed to simulation an AFKing player, so this is normal. To avoid this, you can increase the frequency of the random movements via the script UI - this will increase how often the script will move the mouse/camera, making it more likely that you stay logged it. It may take you a few attempts to find a setting that works for you
As for multiple spots, this is not something the script can do, as it is not the usual play style at sand crabs. Again - it's meant to simulation an AFKing player. There are, however, 4-spots on crab claw isle which may be a good choice for you if you're finding yourself killing the sand crabs too quickly! With 4-spots, you'd have to have quite impressive DPS to start missing out on exp.
Hope that helps,
-Apa