Hadith "Whoever killed a mu'ahad (dhimmi) will not smell paradise" (Bukhari 6914)

For a non-Muslim, the hadith looks good at first glance, but I think it's problematic theologically. Because when you look at it literally, it basically tells you that the Muslim who killed a dhimmi will go to hell. But there are plenty of other hadiths which say that basically all Muslims go to heaven. Also no matter how big was your crime, there is always the option of repentance. Is Allah no longer the most merciful after you kill a dhimmi? And the Muslim scholars actually do "interpret" the hadith as "you can actually still go to heaven", but it just contradicts the hadith.

And Allah forgave to this mass murderer (Bukhari 3470):

The Prophet (ﷺ) said, "Amongst the men of Bani Israel there was a man who had murdered ninety-nine persons. Then he set out asking (whether his repentance could be accepted or not). He came upon a monk and asked him if his repentance could be accepted. The monk replied in the negative and so the man killed him. He kept on asking till a man advised to go to such and such village. (So he left for it) but death overtook him on the way. While dying, he turned his chest towards that village (where he had hoped his repentance would be accepted), and so the angels of mercy and the angels of punishment quarrelled amongst themselves regarding him. Allah ordered the village (towards which he was going) to come closer to him, and ordered the village (whence he had come), to go far away, and then He ordered the angels to measure the distances between his body and the two villages. So he was found to be one span closer to the village (he was going to). So he was forgiven."

So either you can kill a dhimmi and repent and go to heaven - in that case Bukhari 6914 is wrong. Or 6914 is right and a Muslim will go to hell, which contradicts many texts, for example Bukhari 2856: "He should not punish him who worships none besides Him". Not doing shirk is supposed to guarantee paradise. And there are many hadiths like "Do this and he will forgive you all sins. Do that and he will forgive you all sins." And then out of nowhere 6914 totally blocks paradise.

I find the natural explanation to be that the dhimmis fabricated the hadith to protect themselves.