I agree, sometimes it is tough to nail down certain ideas in scripture. Especially those passages that appear in conflict with each other. I will make comments on what my view is on these scriptures below.
The kingdom of heaven in this passage could be referring to this present age of God’s kingdom. Meaning those who follow Christ, but yet live a sinful life and teach other to do the same will not be respected at all. While those who do live righteous lives will be highly respected.Mt 5:19 - Anyone who breaks one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever practices and teaches these commands will be called great in the kingdom of heaven.
Now to continue on with the thought, here is verse 20:
20 "For I say to you that unless your righteousness surpasses that of the scribes and Pharisees, you will not enter the kingdom of heaven.
In this passage I believe Jesus is referring to those who are just like the Pharisees, people who are Christian in name only, who cannot enter the kingdom of heaven in this present age or the age to come.
In this passage there is no place where hell is mentioned. One view of this and it keeps consistent with what I believe is that Jesus is referring to judgment day. Meaning that those who know about Jesus, and have outright rejected him, will receive worse judgment in this life than those who don’t do the right thing out of lack of knowledge.Lk 12:46-48 - The master of that servant will come on a day when he does not expect him and at an hour he is not aware of. He will cut him to pieces and assign him a place with the unbelievers. That servant who knows his master's will and does not get ready or does not do what his master wants will be beaten with many blows. But the one who does not know and does things deserving punishment will be beaten with few blows. From everyone who has been given much, much will be demanded; and from the one who has been entrusted with much, much more will be asked.
For example:
Matthew 10: 12-15 –
12 "As you enter the house, give it your greeting.
13 "If the house is worthy, give it your blessing of peace. But if it is not worthy, take back your blessing of peace.
14 "Whoever does not receive you, nor heed your words, as you go out of that house or that city, shake the dust off your feet.
15 "Truly I say to you, it will be more tolerable for the land of Sodom and Gomorrah in the day of judgment than for that city.
Why would a house or city that rejected Christ’s message have worse judgment than Sodom or Gomorrah? I’m sure you can probably agree that Sodom and Gomorrah was far more sinful in our eyes. However, looking at Luke 12 and matching it up with Matthew 10 you can see that Christ found it more condemning to reject him outright instead of living a sinful life without the knowledge of Christ. Hopefully, I am making sense here. Let me know if you see these passages in a different way that would make it consistent with a multi-punishment system in the afterlife. It just seems to me that all the passages that are clear about hell, none of them give any hint to a diverse punishment system. From a human response I can see why one would want to believe that. Who wants people who are good and descent in this life to suffer the same as people who acted like Hitler? Unfortunately, I just don't see where the Bible proclaims multi-punishment in the afterlife to be true. Thanks for your response.