Take 5 of the cases, charge them with powder and seat a bullet. Use a starting powder charge because you're only checking for function. Fire them. If they go bang, use up the ones you have seated and don't be so forceful the next time around.

There is no "max" depth per se, but you don't want to completely crush the primer. Ideally, the primer should end up right around 0.005" below flush with the case head. If you're seating them much deeper than that, you're likely ruining them or have the wrong primer (large pistol instead of large rifle).

Whatever you decide to do, don't scrap the brass. You can decap live primers without issue. Wear eye protection just in case, and simply run them through the size die (lube the case) or better yet a universal decapping die. Be gentle. You don't want the decapping pin to make a sharp connection with the primer anvil, but steady pressure wil push the primer out without much risk at all of setting one off.