After Ace got the information about the Forbidden Radiation Sea, he instantly contacted the house members and told them about this discovery.
Even they think that the answer really lies past the forbidden radiation sea, so they all head towards it and agree to meet Ace. If it was anyone else, they might not be able to cross it, but it was a different story for Ace.
Qi radiation didn't affect Ace because of his heavenly Qi, so only he could cross it, and he was leaving his avatar here so he could retreat anytime if he felt threatened.
As for the forbidden boundary in the endless sea, he didn't dare to go there because he still thought it was the place where that terrifying existence was locked, mentioned by the sword.
In the meantime, he enjoyed his time with Eva and also raised his remaining skills and laws to the peak.
Of all the skills, his main focus was the Absolute Pick Pocket and the Art of Mind Stealing.