Hello and thank you for your question;
There are different symptoms you are describing that suggest different scenarios.
The worst one rat poisoning, however with this there would be blood coming out from every hole (nose
, mouth, anus etc) and even death
in short period of time.
So if he is not bleeding
from anywhere this is less likely.
Now the shaking of the legs and the "sluggishness" might be an electrolyte unbalance.
Soft stools can be a sign of intestinal worms.
My advice is to keep him hydrate with Gatorade. That way you keep his electrolyte levels.
This will keep him through the night. But the best thing is to test him for worms by your vet.
Again if the shakings stop and he is not bleeding he should be ok through the night. Just follow the above instructions.
Best of luck and im here if youbhave mores questions