That's a hard "No."

First of all, that's not safe for you.  To hand over your metamask account you would have to give me your seed phrase, meaning the escrow agent would have access to, and control of all your accounts. 

Second, it would be unsafe for the lender because you would still have access to the funds and could move them as soon as the lender sends you the loan.

Third, no lender is going to give you a loan based on "Estimated value" of digital art or NFTs.  If you default on the loan, the lender would be stuck trying to sell NFTs that may have no actual value or take years to sell to recover the lent amount.

Sorry, but I have to rescind my offer to help.