Do NOT buy the Air2 ! I have one and I limp along trying to wait until I can afford to plop down another $1000 for yet another iPad. Although the processor of the Air2 seems solid , the screen technology of the Air2 makes it the worst touch screen. It doesn't work well with Bluetooth styluses for example. If you have the money it looks like from everything I read here that people are very happy with the Pro and Apple Pencil combination for art.
When you have the Apple Pencil you should be able to disable Procreate Palm Support because the Pencil has its own palm rejection. I am thinking that the tip of your pencil might be loose. You should only reinstall as an absolute last resort and make sure you have everything backed up if you do that. The size of your gallery should have nothing to do with it I don't think. I sus pect the restart cleared up some kind of iPad problem.