He crowned himself king of the Serbs of Bosnia, the maritime lands etc.

Po milosti gospoda Boga kralj Srbljem Bosne, Primorja i k tomu.

No, you are wrong. Srbljem and Bosni are separated in his titulation. He used the title 'Srbljem' to denote the Serbian throne while ban/king of Bosnia ( Bosne/Bosni) was traditional title  in Bosnia. ;)

In the charter where Tvrtko speaks about his coronation he says that he is crowned with two crowns, one of God-given land of Bosnia and one of Nemanja family. Offcourse, when he speaks about his trip to the coronation site, he says that he went to 'Serbian land' ( srbskuju zemlu). ;)

before his death the title 'kralj Srbljem' was changed to 'kralj Raske' which means that he considered Serbs and Rascians to be the same, the words denoting the same "tribe".

There are charters where he numbers himself among Bosnians ( when I find more time , I will find it for you).

Now I am waiting for Ninoslav's charters and regnum servillie… :D

Most of what you wrote, well… ALL of what you wrote is wishful interpretation of historical facts. I might as well say that your interpretation is wrong, since you weren't there when he spoke about it. It doesn't matter, for that we have historical facts.

Bosnia existed as a kingdom only after the fall of the Serbian empire, as one of the numerous other short-lived regional kingdoms that emerged, every one of them having an own king. Tvrtko being one of those Serbian kings, hence he crowned himself as such.

Srblje are people, while Bosnia, Rascia, Doclea etc. are regions. There are only two people that were enumerated by names, namely, Croats and Serbs. If you find a document speaking of the Bosnian people of Slavic tribal ancestry, I will support it… until then Bosnians are a regional term defining Slavic people that lived in the region of Bosnia, those people were Croats in the north-west and Serbs in the south-east. The same way Rascians, Docleans etc. were for those Serbs living in those regions.

You may interpret a line to fit your fantasy, but you can't change the historical fact that there is no Bosnian Slavic tribe and that king Tvrtko didn't crown himself as the King of Bosnians, Serbs etc. but as the King of the Serbs of Bosnia etc. (Kralj Srbljem, Bosne, Primorja i k tomu)