1. yes you need 2 permit. But what's the logic, you will get off campus work permit after 6 months + 58 days processing days.
2. Its for course duration + 90 days with in which you must apply for a PGWP.
If you withdraw from the school, you will get a refund, not your bank. But you wont get any money for a new school unless you make required changes in loan papers which is very difficult. Loan is based on a risk assessment.
avoid cash and take convertible American Express Traveller Cheques, carry only 20 dollar denomination cash, not more than 100 (Rs. 5400). Visit bank and take your LOA and PP, and apply for a student account and get a debit card, virtual debit card.
your bank will do wire transfer only for the beneficiary i.e., your school. You won't get any extra penny for a new school unless you make suitable change in your loan papers.
you face problem only when applying for an off campus work permit after 6 months of studies because you will have to attach marksheet. But from where you will get a marksheet if you change school and waste 6 months.