Honest question, not rethoric. I don't see how paper ballots get any safer than electronic, it just seems to change what's the easiest approach to tampering.
Using both methods to verify one-another sounds decent though.
2: People watch the box to make sure it's not tampered with as people put their ballots in. (This works to a point with voting machines, although a attacker interacts with a voting machine for much longer than the ~6 sec it takes to drop a paper ballot in a box.)
3: The ballots are taken out and counted, with more watching. Due to physical laws like conservation of mass, it's very hard to make the number of ballots coming out differ from the number that went in, and even changing existing ballots is nontrivial. (Voting machines can silently delete, alter, or add ballots matching arbitrary criteria.)