Thats not a fighter, but a Gunboat.
In this case, why not use a Gunboat engine?
I'll reduce your propulsion by a third, but also cut your weight by 25%. (1 engine 250 tons, having one with double output is -33% power, -25% weight)
Also, having 10% of your ships mass in Engineering spaces isn't that bad, after all, they are a buffer to the important systems if something breaches your armor, and add to damage control.
As for Lasers, once you have Capacitor tech 15, you can build a 10 cm laser with size reduction and 5sec fire rate.
That'll allow your to build a size 2 laser with low energy requirement to be used en mass.
With that high shield tech, I'd probably take out a lot of the weapons to increase the defensive, after all, the parasites are going to deliver the punch.
500 shields will result in 6k+ points of shield that regenerate in five minutes.
As Military History has shown, a lot of guns of a lot of calibers aren't more efficient than a few select in bigger numbers.
That was the success of the HMS Dreadnought, whose name is rather well known sort of today.
Big guns for good range and Anti Armor, small guns for small targets and short ranges, but with higher DPS.