Yes, visible light laser will double the range of your lasers. Near ultraviolet's x3 range. Also, 15 cm lasers are much bett.er than 12 cm. Same size, 1.5x the damage/range. The quickest way to get your laser range past 200k km is 15 cm ultraviolet (x4 range) lasers, for 240k km range. Of course, that's 20k RP in total, and to use it you need good BFC tech as well. Might be a bit expensive for you.
What do you mean, 'can't launch'? Unless you did something with hangers, built fighters should just appear in their own task group, and can then be used like any other ship.
DSTS are just MASSIVE thermal and EM sensors that stack with each other. No active sensors, no res, detection distance is proportional to enemy signatures. = 1000 km * signature * sensor strength. Default start gives you four DSTS * 250 str each = detect a strength 1000 signature from 1 billion km out.