And for what it's worth, I also reduced the size of all the stars in their textures (basically doubling the canvas size then halving the texture size) so the stars aren't so big anymore, either -- then added a star_count_multiplier value of 2 to compensate. Much nicer starfield.
Would it be possible to post any comparison shots? Even with higher star multipliers?
Regarding star textures and framerate - there's Cinematic Sky and Realistic Stars OXP. The former is more stressful than the latter, from what I remember when I tried them. In particular, the nebula textures were a major factor.
As it requires editing the textures themselves, it isn't an easy thing to do (though once you have the textures it's easy enough to change the count multiplier, of course). I'll make an OXP of it, including dust as well as a farther sun position setting. Existing OXP/OXZs which alter sun position, I've noticed, all are using an old value that causes a new feature in the current version of Oolite to be ignored (modern Oolite has varying sun positions on a per-system basis, but current mods like Distant Suns, Sensible Sun, Realistic Stars, etc. are using sun_distance_modifier which makes Oolite ignore those varied distance values, so the best way to make farther sun positions now is to use the new sun_distance_multiplier).
I'll package it all up and write up an explanation as to how to tweak each value so you can customize everything to your liking. (If I knew how I'd make it OXPConfig compatible... but I hear that's supposed to be replaced by some other tweaking method anyway.)