I don't know about anyone being righteous, as scripture holds us all as being unrighteous.
I don't understand what you mean by stumbling stone. What is the stumbling stone?
What I believe about those who are not in Christ Jesus is this, in the resurrection, some will be resurrected to life, because they have done good deeds. But, and this is not negotiable, if one is not in Jesus Christ, has not received the new birth by His Spirit, then they cannot enter the kingdom of heaven. The kingdom of heaven will be inhabited by the children of God, that is, those who are born of Him, by His Spirit. No ifs, ands, or buts.