I thought your primary goal was weight loss, and secondary goal was getting better at the big 3?
Since you describe your current weight as 280, which was what it was a month ago, it appears you are not making progress on your primary goal. Have you considered how much easier pull-ups will be if you focus on your primary goal?
How are your big 3 coming? Not trying to bust your balls, but you may be suffering from the dreaded beginner’s boredom/fantasy disease, where once newbie gains slow down the trainee begins to seek out other arbitrary goals like getting good at pull ups for no particular reason at all.
If you are still committed to your goals, I can assure you there are many top tier powerlifters who never do pull-ups. There are no mandatory exercises. If you really want to get better at pull-ups, then go for it. There is nothing wrong with that. However, if you are doing it because you think you “have to” be good at pull-ups, then please reconsider.