Typically, ship top speeds ought to only be about a third of the speed of light in the case of the ships with the fastest STL drive units. This makes ship-to-ship combat much more liable to take place in a light-second distance than the actual AU (which takes more than 8 minutes for light to get across, like you said, versus the more palatable 300 000 km increments). The most accurate weapons should be beam weapons, then directed beam weapons, and then direct fire projectiles. Guided projectiles are sort of wonky in SARP since some are uber fast, but there's a movement to tone them down to speed slow enough so that pressing the fire button wouldn't mean an instant hit.
But technically, since lasers are supposed to be the 'most accurate weapons', this means that most of the sensors you've outlined in your post aren't quite so useless as they seem.
With Anti-FTL technology, this binds ship battles to much smaller, more manageable distances, fortunately. SARP, though, is quirky with its weapon numbers and many try to make those numbers big to have them feel impressive. I wouldn't worry too much over it if I were you, or else you'll spend most of the time banging your forehead against your desk as you try to make sense of SARP's... lack of universal scaling in the varied technologies it offers its playerbase access to.