1. If you have sufficient funds in the form of FD in the other bank that you are referring to, then, that itself would be sufficient as POF. In that case, submit FD certificate along with a letter from your bank for the FD.
Regarding salary slips for the current job, if you are claiming points for the current job, the document upload instructions asks to upload salary slips (if you have them, but it is not mandatory). However, if your reference letter covers all the points which CIC is looking for, you need not submit salary slips. On the other hand, if you choose to upload salary slips, then yes, you will need to explain your loan and get a letter from your relevant bank which would state the details of the accounts (savings, loans etc) held by you with the bank.
2. You need to show this only if choose to submit salary slips which would show loan dedications. What kind of loan is it, is it a secured loan? However, if you already have sufficient funds, declaring a loan will not affect your application negatively.
3. Either a letter from the bank which covers all the requisite information or else get 6 months bank statements signed and stamped by the bank.
4. I would suggest not to go ahead with that approach as you will have to explain the sudden inflow of funds into your account which would suspiciously look like a loan availed to show as POF.