Beleg,
I understand the difficulties you must have, because
Tolkien's sources and influences as well as his interests were somewhat biased towards the northern Euopean and English (Anglo-saxon) history, mythology, literature and culture, none of which you are probably familiar with. But everyone with English as their first language and/or a (northern- and central-) European background should be familiar or at least interested in these subjects since they represent the historical, philological and cultural "roots" for us.
But also should everyone who is seriously considering to venture into Tolkien-scholarship (and eventually at some point and after certain necessary efforts may be considered a Tolkienologist, but this is IMHO not a title one can claim or gain by passing a nonsensical trivia-test) show some familiarity with those pieces of literary works that have been a major influence for Tolkien.
The single most revealing essay by Tolkien himself, about his sources and influences, but even more so about his judgement what is of essential or central importance for literature in the mythological area, is the lecture he gave 1936 to the British Academy titled: "Beowulf: The
Monsters and the Critics". This essay is - though rather "dry" to read - IMHO worth to be "studied", not only read and understood, if one wants to understand what Tolkien had in mind for his own "mythology".
The single most revealing book about Tolkien's mythology, it's origins and roots is
Tom Shippey's first Tolkien book
The Road to Middle-earth, and even though his second book is more "refined", the first represents IMO the better starting point for this long and labourous journey into Tolkien's world of faeries and myths.
I have also tried to compile a list of Tolkien's literary and historical sources
here.
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Now for your ideas and questions:
The
Hobbit is in my understanding not of central importance, it does not play a crucial role in his mythology either.
Also Tolkien sure is correct when he states (in Letters #25) that his book -The Hobbit -
tale is not consciously based on any other book, rather the book - and even more so the LotR and
the Silmarillion are based on dozens of other books, he had read or studied and his own
tales have evolved from the "leaf-mould" of his memories (as he so aptly put it).
The Edda(s) are the oldest pieces of northern (European) mythological tradition, for reasons I will not try to explain here, he preferred those over the maybe even older existing Celtic myths. The Edda(s) represent
the old Germanic (heathen) mythological traditions that have been destroyed by the Christianisation in Europe, but survived in Iceland. The Poetic - or Older (though it is ironically the younger one)- Edda is a set of poems that have been passed down by oral tradition and written sometime in the 13th century AD, the Prose - or Younger Edda - has been written ~1200 AD by Snorri Sturluson and contains - aside from a "carrier" storyline (IMO similar to the Eriol-story in the LT) prose versions of many of the tales of the Poetic Edda.
Scandinavia is a name for the northernmost part of Europe, originally Norway and Sweden, with the northern part of Denmark, but sometimes Finland, Iceland and the Faroe
Islands are also counted in.
The names of most of Tolkien's
Dwarves are taken from a part of the Poetic Edda, often called the "Dvergatal", I have quoted this part in one of my previous posts. Their meanings are not generally clear (not to me anyway), but here goes:
Thorin: The adjective 'þorinn' (pronounced "thorinn") means "brave". Also, the name "Þór" (Thor) is common in Iceland and refers to the
god of thunder
Thrain is a fairly common name in Iceland (Þrá
inn) and means "stubborn".
Thror ('Þrór') is also one of Odin's (the oldest of the Aesir, the Germanic gods, often called the "All-father" in the Edda

) many names.
Bombur: ('Bömburr') is most likely derived from the noun 'bumba' which means 'belly' and thus 'Bömburr' means '
the one with the big belly'.
Some
other names (
Oin,
Ori,
Nori) probably describe small worm- or maggot-like
creatures, because in the Eddas, the dwarfs originally
were worms (maggots) in the flesh of Ymir, the giant from who's body the world was build by the gods.
A somewhat more complete description of origins and meanings of the Dwarven names will be available at the TolkienWiki soon.
Gamgee (gamdschee) also refers to cotton-wool (c.f. Letters #184 to
Sam Gamgee)