Hopefully, you have time to be with them/observe throughout the day. As a chicken newbie, observation will be your first and best friend in learning all things chicken. Just to cover the bases since you are new to chooks:
- Are the chooks on a balanced feed? (i.e., either a quality layer ration or grower/finisher supplemented with calcium on the side)
- Does your coop/run have adequate space for your chooks? Rule of thumb is 4SqFt coop & 10SqFt run space per standard sized bird.
- Do you have adequate nest boxes for your chooks? Rule of thumb is one nest box per 3-4 layers.
As to you questions/issues, observation will be key to determine who lays what. My observation is fairly Orwellian in that the chooks are subjected to video from just about every angle imaginable in the coop/run but live, real-time interaction is just as good. Time/experience will allow you to determine which hen goes with egg though there are dozens of slight variations in color/size/shape that will constantly test/hone your discernment.
As for getting them laying in the boxes, fake eggs are a great tool that you are already utilizing. Gently placing hens in the boxes with the fake eggs will also help. When chooks see a clutch of eggs in a location, they think to themselves that this must be a good/safe place to lay if others are doing it. Darkening the nest boxes a bit can also help encourage laying there. We did this by putting up "curtains" in front of each box. If you have hens laying outside the coop/run, they will need to be locked in for a few days to cement the coop as designated safe-area.
Cracked eggs can be caused by a number of issues. First and foremost comes back to nutrition. Adequate calcium is needed for strong shells and this calcium MUST come from a always-available source (either a quality layer ration or a crushed oyster/egg-shell supplement to grower ration). If they exclusively free-range, it might be possible for them to get all the nutrition they need from the range but most backyarders don't have the luxury of a healthy and varied range of sufficient quality/quantity/size to support our chooks solely. Cracking could also be caused by where they laying. Nesting material in the boxes is usually soft/welcoming to cushion the blow of the egg dropping out of the hen. If there are laying on the hard ground, this could contribute though shells from hens with good calcium levels are fairly robust and should be able to handle a bit of knocking about. Last thing that could cause cracking is the hens inexperience. There is nobody to explain laying to them and they really do get freaked out the first few times these big, heavy round things start falling out of them. Their attention/dexterity/care when walking around/among eggs will increase with experience and they'll be less likely to knock the eggs about.
Hope this helps. Time, experience and a little guidance by you should get them whipped into shape.