ABSOLUTELY have a space between UNIT and the number. Frankly, I didn't see that as unspaced anyway. WORDS and the numbers that follow are assumed to be spaced. It's print symbols (non-alphabetic, non-numeric) that can be tricky to space.
You're the transcriber and that means you're the boss. But I do think the TN is over-describingg and it wouldn't be done that way by most transcribers. A TN is basically an interruption and an intrusion, no matter how necessary. The idea is to keep them very brief and use only when necessary. It is not necessary to describe the print just to describe it. If you are using arrows and you have listed the arrow symbol, you don't say in a TN that arrows are there. If they're in the braille, there they are. The reader sees them and knows they are there. It's just like anything else. When something is in italics you use the italisc sign. You don't add a TN to describe that italics is there. Same thing with double caps. If a word is double-capped. ANY word, you don't write a TN to say the word is double-capped. You just do it in the braille and the reader reads it.