That's normal, you'll always find a few floating, I generally separated them, and put them in lowered water so they didn't float too much, it sometimes meant minimal water, but it got changed twice daily anyay.
Entirely normal that some are developing front legs before others. When they get noticeably larger than the others separate them, that way you ensure the smaller ones get the food they need.
How are you going with the brineshrimp separation? I turned of the airpump, let as many eggs settle or rise, as the case may be, then turned a desk lamp on and aimed it towards the bottle/tank and it was pretty easy to suck up the brineshrimp that gathered towards the light source without collecting any eggs. I used Cloth's method, of hanky over a jar, squirted the brineshrimp into it (salt water went in jar), then rinsed with dechlorinated water.