My personal favourites are Slingshot work and Reverse Band work. Boards are great too for some people, I don't like them as much just personal preference.
From looking at your videos I think you'd do well to get in some additional upper back and lat work too and just work on your form, staying tight etc. Your set-up could do with being tighter and that would help the smoothness of your bar path. It tends to be a little wobbly at times.