As far as this OLD 43 yr old mind can remember,,

i believe Kent salt WAS made by Instant Ocean,,,,,don't think you can do wrong with it,,(might be the same thing)
on the "crusty salt"(no , not YOU Jerel,heheh

), as long as it's a bit and it's not THAT hard (that you can't break it up in your hands) it ought to be ok,,,i'm assuming that you use aeration or a power head in your make-up container to mix the salt ... just remember to keep the bag/bucket closed up when not using it, and away from water/moisture til you need it,,