Can I remove that huge time stamp from the lock screen or make it much smaller by changing the font?
No, you can't. That's the way Apple has designed it, so that's the way it has to say.
On the plus side, it's designed this way so you can quickly glance at your lockscreen and see the time, even if your phone is at waist height (or further).
perhaps if Swipe up on the locked phone to get to the control panel there can be some customization?