With few exceptions, absolutely not, it would actually hurt you if you still got xp from those TVHM bosses. It can be worth doing specific farms at level 50 immediately after killing the Warrior and before actually starting the UVHM playthrough. You don’t have to, but if there’s something specific that you really like and think will help get started in UVHM, go for it. Just bear in mind that any level 50 gear you get will be of dubious value by level 52-53, and completely useless by 54-55. Based on your previous post it sounds like your character is above level 50, so going back to TVHM to farm anything would be a bad idea at this point.
DLCs - you’ll want the four main DLCs just for the content and story. The Marcus Saves Mercenary Day headhunter DLC is also well worth getting. The other four headhunter DLCs are optional, get them if you want them but you’re not missing much if you don’t. You almost certainly have both UVHM packs since you mentioned running Digistruct Peak in TVHM (I didn’t know that was possible - I assumed it was level 72 only!).