I think that instead of trying to convert the unbelievers, the Pope would do better to court the protestant churches and to try to convince them to rejoin the catholic line. He may be only 1 sheep of a 100, but the 99 are still mostly christian believers, they just aren’t catholic. In particular, he should more forcefully address their sola fide and sola scriptura doctrines. If he presented concrete scriptural evidence for the necessity of good works and of the sacraments, and presented it directly to the ministers of the protestant churches instead of their constituents who listen to the ministers before the Pope, the reunification of the church just might happen.
Unfortunately, Scripture doesn't agree with him on those subjects, so he wouldn't be able to use them. As far as good works go, they show faith, they don't accrue salvatory credits or merit, that has already happened through Christ.