Lender offers a rate w/ 0 pt/0 fee. Should the GFE (Good Faith Estimate) include lender's refund/credit to reflect that offer?

Ask for a breakdown of the settlement fees at least as to category. That will tell you if you are actually paying a hidden points or commissions.The will be fees associated with any loan for title and escrow. No. You do not have to take the offer unless you have already obligated yourself. Simply having a "lock" will not normally obligate yourself.