The kodi.log you've been posted says at line 54 and 55:
This will change when you use advancedsettings.xml to increase the log level.
Line 41 to 50 of your kodi.log quotes your current advancedsettings.xml, so I think it has been loaded fine. If it has no effect on some of your settings, then LE ignores them for whatever reasons.
If you could post another kodi.log at log level 2, then we maybe find answers.
If you use network streaming, then playing the same file from an USB stick should be the first thing to try.
I think you have to contact with support team. They have a proper knowledge to assist you in proper manner.
Very funny, this IS the support team. Our community provides better service than most commercial companies.
You can verify this by changing the log level from 0 to 1 or 2. That will be visible at kodi.log. Read here how to change the log level.
Do you have a link to the type of HDMI splitter you're thinking of? Is it something like this: eSynic 1080P HDMI Audio Extractor Splitter HDMI to HDMI + Optical TOSLINK SPDIF + Analog RCA L / R + 3.5mm Stereo Audio Splitter Adapter Converter for TV Blu-ray DVD Player SKY HD Box PS3 PS4: Amazon.ca: Cell Phones & Accessories
I don't suggest it. It's not future-proofed, because it doesn't support 4K. I found this splitter, which supports 4K and CEC: FeinTech VAX00102.
PS: If you additionally buy a 90 deg. angle adapter (Ebay) and use a 90 deg. power plug, then you can do a 180 deg. turn at the front of this splitter. So your studio desktop will look well-organized. The ability to switch off video while still having audio is another plus for a studio.
Thanks. The other idea I was thinking of was to get a HiFiBerry DAC that would plug into my raspberry pi.
That's an option, but the HDMI audio splitter is the more universal tool, often has optical output and might be cheaper. The only bad thing I heard about those splitters is that some of them don't pass-through CEC signals.
PS: Don't expect to get all audio formats (incl. AC3, HD audio etc.) when using a HiFiBerry DAC. The RPi's data bus will set some limits, too.
We usually don't see music production equipment here, so chances are very low to find another user of this hardware.
Anyway, there are some facts about USB audio and LE. Generally spoken, the higher the audio data rate, the lower the chance that an USB DAC will work. LE is no real-time kernel system, which will make USB transfer slower - too slow for some audio formats. Current user reports say that AC3 is kind of a breaking point: Audio formats below such a data rate work, AC3 and better doesn't work.
NI is a company for professional musicians, so I bet your device wants to receive USB audio data by using a pretty high data rate. If you find settings to reduce audio data quality, give it a shot.
My advice is to forget USB audio, and use an HDMI audio splitter instead. Then connect your NI device by using a cinch cable.
ps: in case i would anyway try to make kodi run correctly on my hw... i would need to patch the stock kernel, right?
Follow the suggestion of the linked thread instead, and install Ubuntu. Ubuntu's repository provides Kodi.
So does AC3 have more data rate compared to DTS ?
That's very likely. It's on you to do an internet research and find the bullet-proofed answer. The specs must be somewhere. At the moment my theory is based on the thread I linked above.
Please always use the search function before starting a thread. Click.
I think the issue is a too high audio data rate. It seems like AC3 is too much data for the data bus, resulting in data loss. Read here.
If you must have AC3, then buy an HDMI audio splitter.
No. Some people use extra hardware to switch on by RC.
Same error when using the default skin?
I pretty much do exactly that every day at work.
That's cool, then you're an expert in multimedia routing. Unfortunately your NUC is probably far away from the hardware capabilities you're using at work. To be precise, I don't think the NUC's data bus is able to stream A/V data to TB and HDMI in-sync.
I know that other LE users failed to use an USB DAC when it's about high speed (HD) audio. LE's Linux is no real-time kernel. On most hardware HD audio can't be delivered in time to USB, so audio data will just be dropped by the system. You will run into problems like this if you try to use TB and HDMI at the same time for A/V output.
I bet it's impossible to get A/V on TB and HDMI at the same time. So you can't grab audio from the NUC's HDMI output, and the HDMI audio splitter solution still seems to be the best. Wow, there are some crazy dependencies among BIOS, kernel and Kodi. I don't want to deal with it. That's why you live in Silicon Valley, and I'm in Germany. 
Thanks for testing the autostart.sh line.
Just to be sure you tried the right config.txt options, add this lines to the above:
It will start your RPi at 720p / 60Hz, fitting for your monitor specs and RPi speed.
He will not benefit from selecting a separate audio device, because HDMI is his only digital audio output on the NUC.
The NUC does not allow to use Thunderbolt as an audio-only device, so it's not available as Kodi audio device.
I'm reading here for a while, but I never heard about such a routing option. Buy an HDMI audio splitter and go optical to your receiver.
