I think that everything is quite clear if one keeps in mind the distinctions made by St. Thomas (and many of the Greek Fathers thought the same way) ...
Natural Order -- you get punished for actual sin, but also rewarded for exercises of natural virute (at lest in the sense of having this remit the punishment due to the actual sin)
Supernatural Order -- nobody deserves it, and there's no injustice or "punishment" involved in God not granting this gift to anyone, and it's not contrary to God's Justice or Mercy to deny it
On the natural order, if you've committed no actual sin, you are not punished, and you can have natural happiness. If you've committed sin, then the punishement due to it can be mitigated by acts of natural virtue.
On the supernatural, there's Original Sin, and there's nothing we can do to get that back other that God's free gift of allowing us to receive the Sacrament of Baptism.
If kept separate in one's mind, there's no issue with people who have committed very little sin not being saved, since it's owed to no one anyway, and the degree of their happiness or unhappiness in Heaven depends upon what they deserve due to their actual choices and acts of free will.
Reward/Punishment for actual sin happens by our activity -- ex opere operantis
Supernatural Reward/Punishment happens only by God's free gift via the ex opere operato action of the Sacrament.
There's no strict overlap between the two except that God might regard someone's natural virtue in terms of deciding whether or not to bestow the gift of Supernatural Reward, but there's no direct correlation, along the lines of the BoDers mentality, "oh, but he was such a good guy, generous, selfless, kind, and he even gave his life to save someone else in a disaster situaiton" ... ergo he deserves the Beatfic Vision. False. We do not know how/why God decides such things any more than we know how/why God decides to have someone born into a tribe of Great Thumb worshippers, and another to be born into an extremely devout Catholic family. There's too much of this second-guessing about what would be "fair" and "unfair" for God to do ... by us pea-brained morons, and it's that attitude that has led to BoD speculation. "Look, this catechumen was so devout and virutous, and tried so hard, but he died before Baptism ... but then this jackass over here waited til his death bed to be baptized since he wanted to keep living an immoral life, and he got the Sacrament."