Beam weapons affects only capital ships.  SF and HC attack damage is affected by "wave" attack upgrades, which are a separate upgrade line.

As far as pin-point bombardment goes, the biggest problem is that moving a few paces closer is virtually free to begin with.  There's no real use for extra range.  It's not even like LRMs where there are actually static units you want to be able to shoot from outside of retaliation range.

Well, I never really build turrets, but I can see a situation where someone rings the planet with them at low orbit to protect against siege firgates, and the point of an upgrade which would then allow siege frigates to fire from outwith turret range.  I have no clue if the upgrade is significant enough to allow for that, since I haven't built siege frigates in ages (though I have been trying them a bit with the latest patch).  If I use anything it's hanger bays with fighters to protect from siege, and against that extra range does nothing except a slight dps gain (if you are comparing damage to time-in-system).  So, yeah, still with you on the upgrade being pretty damn worthless.