I'm 99% sure your inability to spectate when dead isn't caused by ULX (or it's noclip), and is most likely a server setting (or is another mod/gamemode conflict).
As I have no TTT experience, are you _sure_ you're supposed to be able to fly around/spectate?
I only question because when I die in Sandbox, I'm 'attached' in 3rd person view to my body.
Unfortunately, I wouldn't know where to tell you to start looking.
If another of your mods is watching for player death, then it is most likely breaking the game mode spectate portion.