Right now I'm busy getting caught up with all the reading I missed during my absence but I did promise a translation so here is the quick and dirty. To be honest I think I went way overboard here. Some words of Dragonish would have been fine as the final clue that yes, dragons are not just an unusually large animal. But when line after line are in, it just becomes a chore for the reader. Not to mention that I could have gotten away with Spar just narrating that it said something but she didn't know what, because she's as clueless as the reader is. Anyhow, let's just get started.
PS: as for Fist. I'm obviously not following the game progression of zero to hero with anyone. Spar is pretty insane for one given the chance and Fist is far far above the powerlevel a player is expected to have during the first dragon encounter. (Incidentally, the game helps out by giving you half a dozen archers to help out, and an immortal battlemage kinda woman. So it is very much possible to kill said dragon by hiding in the (indestructible) tower and twiddling your thumbs.

Alright, translation time. For reals this time.
Also, just because I have to mention it. Dragons seem to suffer from a bad case of capitalizing every single word. Maybe it is because they're always so loud. Also, there is no way to distinguish between the various forms of possesive. So my/your/his/her etc all get the same extension. Fortunately as the writer I know the context so I get to cheat.
"Tafiir Nikrin." The first words are said when Spar's (lousy) disguise fails.
(
Tafiir - Thief) (
Nikrin - Coward)
"Roti Nimuz. Rah Niwahlaan! Daedroth! Taazokaan Nisuleyksejuni!" Ok, this is a mouthful. It's the reply to Spar yabbering at it in Daedric. Also probably the last bit of Dragon that would have been necessary
(
Roti - *your* words) (
Nimuz - not men) (
Rah - gods) (
Niwahlaan - not to create) (
Daedroth - Daedroth, it's not a dragon word but eh, whatever. It was what I'd built the rest of that outburst around.) (
Taazokaan - Tamriel) (
Nisuleyskejuni - not your dominion)
Since this was a pretty long thing, let's put the translation all together again to save you the trouble.
"Your words not men. Gods not to create! Daedroth! Tamriel not your dominion!"
We skip a few paragraphs for the next bit (huh, maybe I didn't write down as much incomprehensible nonsense as I thought I did). Anyhow, Nords throw rock and say manly words. Dragon is understandably pissed.
"Dukaanu. Ahraani."(
Dukaanu - your *plural* dishonor) (
Ahraani - my wound)
"YYYOOOOLLLL!!!" dragon spits fire
(
Yol - fire) Sometimes words and action are quite a literal thing with dragons
Spar stabs dragon and we get the following:
"Mal Sahlo Mun. Werid Nosi. Vikkil."(
Mal - little) (
Sahlo - weak) (
Mun - man) (
Werid - praise) (
Nosi - your strike) (
Vikkil - your defeat)
Put together again: "Little weak man. Praise your strike. Your defeat."
I also just saw that
Sahlo while listed in the UESP dictionary as a single word, can also be the words
Sah and
Lo, in which case it would be (
Sah - phantom) and (
Lo - deceive) Interesting and surprisingly applicable.
No more from the dragon, but a wild, shirtless, sweaty total machoman arrives and spouts some more.
"ROH-DAAAH!"(
Roh - balance) (
Dah - push) We assume that Spar actually missed the (
Fus - force)
"fus-ROH-DAAAH!" - "force-BALANCE-PUSH" And things go flying.
Not content with just hammering a big firespitting killing machine against the ground, he follows up with some good old-fashioned trashtalk.
"
Dov!" He says,
"Rotmulaagi Zol Mul."(
Dov - dragon) (
Rotmulaagi - my word of power) (
Zol - most *also could be zombie*

)
(
Mul - strong/strength)
"Dragon! My word of power most strong."
And finally we have a Thu'um that does not exist in the game but which I made myself by putting together a trio of words. I personally think it is quite fitting for (not so) Silent Fist.
"Haal Krii Slen!"(
Haal - Hand) (
Krii - kill) (
Slen - flesh) I thought of doing
Haal Krii Dov(ah) first, but I don't like how specific that would be. So yeah, another example of very literally interpreted dragon-speech.
Wew, that was a mouthful. Hope it's been of some use to everyone.
(Note to self: Be careful with copypasting this. You wrote it right above the characterlist spoilerversion)
Ah, before I forget. Have a belated merry christmas and an early happy new year.