Since you said ‘realistically’ let’s assume it’s using wormholes (which are in fact “possible” arrangements of spacetime in General Relativity). Note that actual wormholes would not be flat, they would be spheres, but that’s besides the point.
Best number I could find for the energy needed to hold a person-sized hole open is from Here.
“negative mass-energies on the scale of Jupiter are required (-1.898 x 10^27 kg)”
Note that we don’t have a method to produce Any negative mass (antimatter is still positive mass-energy).
There are things like the Casimir effect but you can’t take that negative energy and move it elsewhere or concentrate it as far as I understand.
So the answer to your first question already puts this Way out of the realm of having meaningful answers to the others.
Since you said ‘realistically’ let’s assume it’s using wormholes (which are in fact “possible” arrangements of spacetime in General Relativity). Note that actual wormholes would not be flat, they would be spheres, but that’s besides the point.
Best number I could find for the energy needed to hold a person-sized hole open is from Here.
“negative mass-energies on the scale of Jupiter are required (-1.898 x 10^27 kg)”
Note that we don’t have a method to produce Any negative mass (antimatter is still positive mass-energy).
There are things like the Casimir effect but you can’t take that negative energy and move it elsewhere or concentrate it as far as I understand.
So the answer to your first question already puts this Way out of the realm of having meaningful answers to the others.