Be careful focusing on form with just the bar or 25s on there. The bar will be lower to the ground, creating a deficit, and it will alter your setup. Once you get your form down and establish a 1RM (via actual 1RM or calculated) I would jump on a program that will allow progression in your lifts such as 5/3/1 or 5x5. Your core lifts will skyrocket, and you'll get your high rep assistance work.
Don't worry about not hittin that number on lat pulldowns. That's not exactly an exercise I'd track PRs with. Replace that will pull-ups![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Don't worry about not hittin that number on lat pulldowns. That's not exactly an exercise I'd track PRs with. Replace that will pull-ups