I agree with Scotty. It's hard to tell from the picture - I'm not too worried about some variation in floor coloring as such, you may be OK notwithstanding it never hurts to do the acid washing again unless you are seriously under the gun time wise. Even then, the old adage "there's never enough time to do it right, but there is always enough time to do it over" may apply. Surface prep is boring and time consuming but it's 75% of the job.
100 grit is often used as a gauge for adequate concrete prep but is probably pretty deep profile (quite rough) for a thin coating (industrial floors can be topped with 1/4" or 3/8" caps in certain conditions and 100 grit is often referred to for them as well).
But, using sandpaper grades is a good gauge. Compare the surface to 150 grit - if you're there you should be OK.
There is actually an ASTM standard - ASTM 4260 - that speaks to using acid etching. I just checked it - it does not specifically refer to a number of the grit texture, only that it be "medium to coarse". 150 grit meets my definition of "medium". Again, for a thin film coating less "bite" is require than for a 1/4"" topping.
