That is a creative idea, but it won't work. If the contract states that he can not change the password, then if he undertakes any actions to circumvent that restriction, the other side could then file suit against him for "intentional interference with contract".
So the long and short of it is that if the company has violated the contract in any way, his recourse would be to file suit against them for breach of contract and seek damages. But if he takes any actions that would result in a breach of the contract, either personally or otherwise, they can hold him liable.
Additionally, if he transfers legal ownership of the account, the transferee would "step into the his shoes" and be similarly bound under the contract restriction.
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