I will answer your question part by part.
Negative and Positive characters
The CAT score will be calculated as per the formula, S = 3R - 1W, where S is the CAT score, R is the number of right answers and W is the number of wrong answers. Negative marks will be given for each wrong answer. In case of a tie, the existing University norms will be followed.
Chances for EE and EC
Yes you might have a chance with the mark given.
Upto what mark
That depends on the demand of seats on CUSAT CAT.
Caution deposit
The caution deposit for B.Tech.(Civil Engg., Computer Science & Engg., Electrical and Electronics Engg., Electronics & Communication Engg., Information Technology, Mechanical Engg., Safety & Fire Engg.) is 1000 Rupees. you can pay full fees at the time of admission/counselling.
#appreciate the effort !