Are the interest rates fixed or variable during the loan term?

The rates are variable and range between 5-12% APY. The average cost of capital per year right now is about 8% - 9% APY - so that's what you should care about if this is a longer-term loan for you.

If they are variable, what factors influence changes in the interest rate?
The market demand for loans sets the interest rate. Generally in bull markets for crypto the rates are higher.

Transaction Fees and Limits:

Are there any fees associated with setting up or maintaining the loan?
There is a fee of 1% per year on collateral.
There is a small fee associated with pulling capital out (~25 bps) for wrapping and unwrapping BTC. 

Are there any limits on withdrawing or transferring the loaned funds, especially when transferring them internationally?
No limits.

Loan Disbursement:

Clients can borrow USDC funds but if you’d like it converted to USD please reach out to support@abra.com and the support team would be happy to assist.