Instead of a single massive reactor, instead I'd design one that provides enough power for a single turret then just add one per turret on the class. Not only does this stop the wasted space you have on the jump ship but it also gives some redundancy as if your reactor is taken out you loose all power and so can't fire, while if a single turret reactor was taken out there is still power to fire albiet at a reduced rate of fire.
Get your jump ship up to 10,000 tons, use empty crew quarters if you need to.
You have a good level of engineering spaces, enough to make reasonable field repairs and a long maintainance life.
Five armour is not bad for a light beam brawler, but expect to take casualties if you have to survive performing a jump point assault. You are really only going to be able to improve this via researching your armour tech.
You have from my view a somewhat excessive level of fuel carried. Drop it down to 100,000 liters on each ship and have a fuel tanker/maintainance supply ship acompany the destroyer group. It can be detatched and left on the near side of a jump point before you jump and the carried supplies will let your destroyers repair damage without reducing their maintainance life. The saved space along with the 150 tons you have before you hit your jump size limit should be enough to get another layer of armour.
Your destroyer has a surplus r100 sensor. Actually I'd be inclined to drop the r100 sensors entirely from the destroyers and make the r1 larger to fit whatever space you have left on the class. You will only see missiles at around 11% of the listed range of your r1 sensor, so increasing it's range allows you to pick them up further away which also allows time for your missile tracking bonus to build up. Create a sensor variant of the destroyer with one less turret but with a r100 and r16 sensors and large thermal/em sensors. You could do this on the jump tender by getting rid of the extra fire control but it's slow speed would hamper the destroyers from operating in-system.
I'd cut the firecontrols down to 2x range, then mount 2 of them on each ship. While you will lose a bit of accuracy at you max range, that range is small enough that you should really be able to move up closer to a target ship while firing, as you are not going to be outranging anybody.
A priority research should be upgrading your laser frequency from visible light. You need your lasers range to be over 150,000 km to stand a chance of getting two shots off at missiles traveling at 30,000 km/s. As it is you should probably be setting your firecontrols to final defensive fire rather than area defence.