I mostly agree with Mini's points, some additional observations below.
There is not a lot of point in using 50% thermal reduction on engines for a ship this big, you are still going to be showing up on reasonable passives at fairly long range.
Increasing the engine size makes it much more efficient. If you also strip out the thermal reduction this gives.
Engine Power: 600 Fuel Use Per Hour: 180 Litres
Fuel Consumption per Engine Power Hour: 0.3 Litres
Engine Size: 50 HS Engine HTK: 25
Thermal Signature: 600 Exp Chance: 10
Cost: 300 Crew: 50
Materials Required: 0x Duranium 300x Gallicite
Military Engine
Development Cost for Project: 3000RP
This burns 180 fuel per hour compared with 5*64.8=324 fuel per hour for the same tonnage using your size 10 engines, 80% more efficient while also being 33% cheaper.
I'd agree using lower engine power multipliers for elements that are part of the fleet train is a good idea, although I almost never drop the power below x1.0 for any ships I expect to actually fight.
Thermal reduction may actually be of use here as a fighters thermal signature is small enough that sneaking in close is a reasonable prospect.
If we replace your 4 size 1 engines with a size 4 engine we get.
Engine Power: 84 Fuel Use Per Hour: 196.01 Litres
Fuel Consumption per Engine Power Hour: 2.333 Litres
Engine Size: 4 HS Engine HTK: 2
Thermal Signature: 42 Exp Chance: 17
Cost: 63 Crew: 7
Materials Required: 0x Duranium 63x Gallicite
Military Engine
Development Cost for Project: 630RP
Fuel use is 196.01 per hour versus 4*50.54=202.16 per hour slightly over 3% more efficient. This is small enough that multiple fighter engines remains a viable choice.
Unlike Mini I'd recommend keeping the maximum power multiplier. Speed is king for missiles, and fuel usually remains a fairly small size required as long as you are not trying for extremely long range. If you do want long range instead make a two stage missile, with a low power, long range first stage and a max power, low range second stage with the warhead.
You definetely want to design specific missile engines for each size of missile though, as the diffence in fuel efficiency is enormous.
You
really don't have high enough tech sensors to be putting actives on AMM's, I'd even be doubtful about putting them on ASM's. Research up your EM sensor tech to at least 11 and another couple of levels of active sensor strength before putting active sensors on your missiles, it is currently crippling them.
By not placing a sensor on the missile you can create
Missile Size: 1 MSP (0.05 HS) Warhead: 1 Armour: 0 Manoeuvre Rating: 22
Speed: 21000 km/s Engine Endurance: 4 minutes Range: 5.6m km
Cost Per Missile: 0.7425
Chance to Hit: 1k km/s 462% 3k km/s 154% 5k km/s 92.4% 10k km/s 46.2%
Materials Required: 0.25x Tritanium 0.4925x Gallicite Fuel x26
Development Cost for Project: 74RP
Using
Warhead 0.25
Fuel 0.0104
Agility 0.2396
1 size 0.5 engine
Slightly faster, slightly less accurate, shorter range but still perfectly sufficient for an AMM and 1/5th the size. A size 1 launcher for this will also be firing every 10 second instead of every 40, so improved rate of fire as well.
You fighterwork missile is pretty good as a standard ASM. I'd personally use a size 6 missile like this.
Missile Size: 6 MSP (0.3 HS) Warhead: 9 Armour: 0 Manoeuvre Rating: 19
Speed: 17500 km/s Engine Endurance: 49 minutes Range: 50.9m km
Cost Per Missile: 4.5826
Chance to Hit: 1k km/s 332.5% 3k km/s 95% 5k km/s 66.5% 10k km/s 33.2%
Materials Required: 2.25x Tritanium 2.3326x Gallicite Fuel x468.5
Development Cost for Project: 458RP
Using
Warhead 2.25
Fuel 0.1874
Agility 1.0626
1 size 2.5 engine
Which is somewhat faster and longer ranged, but more importantly fits neatly into a capacity 18 magazine, which can be fairly easily researched.
As has already been said, your blockbuster missile is only likely to be effective against targets with no anti-missile capabilities.