Kinetic Energy at High Velocities
If you design a universe that permits faster than light travel, you will need to invent laws for how kinetic energy works when traveling faster than light.
For centuries, we used the Newtonian formula for kinetic energy: $KE = \frac{m v^2}{2}$. And that worked well. It isn't wrong; it's just an approximation that only holds for velocities well below the speed of light.
But for high velocities, we need to use <PERSON>'s version instead: $KE = \frac{m c^2}{\sqrt{1 - v^2/c^2}} - m c^2$. (m is the rest mass in that formula, not the relative mass.)
We could also use this for low velocities if we wanted to; it's approximately equal to $\frac{m v^2}{2} + \frac{3m}{8}\frac{v^4}{c^2} + \frac{6m}{16}\frac{v^6}{c^4} + ...$, so all terms except $\frac{m v^2}{2}$ will be very close to zero. But for that same reason, we don't need to bother with any term except the first when $v << c$, so it'd be overkill. We instead use the simplest approximation that works well at the sort of speeds we're looking at.
Now let's look at what those equations mean in practice. Suppose we have a 1 kg mass and see how much energy these predict at various speeds.
Low speed: 10 m/s
If it's moving at 10 m/s, then using the Newtonian approximation, we get a kinetic energy of $50 J$.
If we use the Einsteinian version, we get $50.00000000028 J$. Both versions are exceedingly accurate, and so we might as well use the simpler one.
Relativistic speed: 0.99c
The Newtonian approximation gives us $3.64 \times 10^{16} J$.
The Einsteinian one gives us $2.58 \times 10^{17} J$.
The Newtonian version is eight times too small; at these velocities, we can no longer use that approximation.
FTL speed: 2c
The Newtonian approximation gives $1.8 \times 10^{17} J$, but we don't care because we've long since passed the velocities where it's remotely accurate.
The Einsteinian approximation gives us $-1.038\;i \times 10^{17} J$. Since our kinetic energy is now both negative and imaginary, it's safe to say that this approximation is no longer accurate (or even meaningful) at faster than light velocities. 512
(It's not even defined at exactly light speed; there's a division by 0.)
In our universe, the Einsteinian equation may not be an approximation; it may be completely accurate at all velocities for all we know. But if FTL is possible in your universe, than it must be an approximation that is only valid at low speeds.
I can't tell you what equation you should use for calculating kinetic energy at FTL speeds; I can just say that the one you're using will not give accurate results in our universe, and the best approximation known to modern science for our universe doesn't even permit FTL, so that won't be right, either. Decide how you want kinetic energy to work at FTL speeds, and then be consistent.
Energy Scale
You don't actually have to make up a new equation if you don't want to, though. You can safely assume that Newtonian physics hold at any velocity in your universe without creating the sort of problems that you're envisioning.
$10^{13} J$ may sound like a lot, but that's by puny Earthling standards. We've tested nukes that are 20,000 times larger than that, and we're all still here.
Let's consider something with a bit more energy than a mere hydrogen bomb. Suppose that Newtonian physics holds at high speed, and that we've got a ship the size of the Titanic moving at light speed. It would have a kinetic energy of $2.337 \times 10^{24} J$. That's a decent amount of energy, but it's 100 times less than the Sun outputs every second, and 100 million times less than what we'd need to blow up the Earth. (Which in turn means that the scene you mention was not the most energetic event we've seen in Star Wars.)
To put things into serious perspective, a supernova can output $10^{44} J$. That's $10^{20}$ times more than our ship's kinetic energy. 921