The Notwithstanding clause is not a get out of jail free card.  If he won the settlement the most the government could do is refuse to pay and then be taken back to court to enforce the judgement.  

The Notwithstanding clause can be used to create a law to violate someone's rights - famously the only usage is to allow the primacy of French in Quebec  It cant be used to avoid a settlement when the Government has already violated someones rights.