I don't think your problem is the striker. If you had only light strikes, perhaps. But, the strikes are off center, meaning the cartridge wasn't presented in full lockup, the primer wasn't centered in front of the firing pin.
At the very least, with that many rounds through the pistol, the RSA (recoil spring assy) should have been replaced several times by now, and may be due again. While a weak spring can cause FTF/F's, the combination of an otherwise tight fitting round (such as many Underwood rounds) and a weak spring is a recipe for FTF's. Glock recommends about 5K rounds between RSA replacement. In my experience, about 3K is more realistic, especially if the pistol is used for any form of defense, on duty, concealed carry, or home. They are cheap and readily available, so no reason to not replace them regularly.
Life is tough. It's tougher if you're stupid. -- The Duke