Absolutely do not sign a Unconditional Final Waiver of Mechanics Lien and Claim without being paid. Once you sign that form, you will have waived your lien rights even if the customer never pays you. There is another form called a conditional final waiver of lien which states the total amount you must be paid to satisfy your lien but it does not become effective until you receive actual payment. You can also tell that customer that you will come the lender with the customer and exchange the waiver for a direct payment from the lender.
The language that you are quoting sounds somewhat like a conditional waiver of lien, but the title says "Unconditional" so there is some issue there. If the amount you are owed is enough to matter to you you should consider consulting an attorney.
You really need to hire a lawyer to look at the document and consult with you. There are several other questions an attorney would need to talk to you about before he or she could give you a reliable answer.