How high are the notary fees for drawing up the purchase contract?

Of course, you need the form from the bank. You can't just register the local savings bank with any amount.

Of course you can. You can simply go to the notary and have a land charge registered for whoever you want. With certificate or without. Whether the bank is satisfied with what is registered (amount, interest + ancillary services, personal assumption of liability, etc.) is another matter.