I'm glad he turned down the prez's offer.
His whole deal is wanting a normal life after being worked like a slave by his family.
Yes, Asuka and Co. might have been nicer, but the moment they all realized he could do everything they would have started exploiting him more and more - that's just how that business works, and he still doesn't believe in his own abilities after being belittled for his whole life up to that point.
Plus, he had no one there to actually advocate for his best interests without bias if he were to get a contract worked out or something, since he doesn't know his own capacity and wouldn't be able to accrurately gauge whether he was being taken advantage of or not.
However nice those people might seem in comparison to his old "employers", they would still be looking to exploit his abilities - even Asuka lied to him from the getgo, asking him to "do some work for her" only to spring on him at the last moment that it was her entire group, and for a high-stakes gig.
Absolutely the correct decision on his part. Hopefully, he actually listens to what they said in terms of recognizing his ability, and hopefully that gets repeated constantly until he comes to believe it.