Yeah it has to be dry to remove from the form. It will crack every time if it's wet. I have never used sawdust for anything like this, so I don't think that has anything to do with it.
Just think of a regular sheet of paper  You can pick up a dry sheet of paper and fold it or crumple it easliy, but a wet sheet of paper will fall apart in your hands if you try to manipulate it at all. Pulp is pretty much just a super thick piece of paper so the same principle applies.

I think the cracking you see during drying is more due too the amount of water in your pulp. You said that it is really wet and you don't aqueeze it for fear of lumps. The more something has to dry, the more likely you are to develop cracks. It has to do with the drying rates of different portions. Since it's almost impossible to make sure this handful of pulp has the same water content as that handful of pulp, the two are going to be more likely to develop cracks. Also thicker layers are more likely to crack as the outside of the layer will dry more quickly than the inside layer. Drying shrinks the pulp and and this is what is causing cracks.
Have you read the tutorials about making pulp on this site?  They are very very good, and you will see that they advise to get your mixture as dry as possible. Not only does this help prevent craks, but also speeds up drying.
The chalk is a filler, and I think the ground up chalk you are using should work just as well as the purchased powdered chalk if used in the proper portions.
Keep experimenting. Everyone has a slightly different method, and use them for different reasons. Start with one of the tried and true methods  and tweak it until it suits your style. That's what makes the medium so much fun, there is no wrong way to paper mache!
Joey

Patience, patience when waiting for the stuff to dry.  I WISH I HAD MORE PATIENCE!!!  If you have a small fan, it should help it to dry faster.

Sawdust has no strength, it's just a filler.  You know how strong wet sawdust... isn't.

Paper pulp is very weak until it's dry, as it's the adhesive that is holding it together, and the adhesive only holds it when it's dry.  All PM seems to shrink when it dries, but even as it's shrinking, pulp is still very fragile, and will sometimes warp as it dries.  Heat increases warping in any PM.

Paper strips have more tensile strength, and you can sometimes handle it carefully when still damp.  If you use it to line a mold (like a bowl), as it dries, you will see it pulling loose from the mold.

Just keep trying and you'll see how it all works, or doesn't.  Practice makes perfect, or nearly-perfect, anyway.

Sue

I have seen wet/fluffy pulp vacuum bagged over a plaster mold; vacuuming both extracts moisture and applies pressure, compressing and forcing pulp into details.

A few suggestions to add to the above good advice:
Work in thin layers - they dry quicker and more consistently than a thick layer.  If you don't smooth them down too much there's plenty of texture for the next layer to grip onto (if you're really worried, paint on some diluted pva/white glue before putting the next layer on).  When I was making bowls I alternated strip layers with pulp, for the reasons given above by CatPerson. 

Make it easier to remove from the moulds - if they're bowls presumably you don't have too much detail to negotiate.  If you start with a layer of wet newspaper (no glue, torn into small enough pieces to fit the mould neatly - it'll stick together enough with the water for this purpose) and then pulp on top of that, you should find it comes off the mould more easily when it's dried.  Vaseline is sometimes recommended as a release agent, to be honest a basic cooking oil (I wouldn't waste the extra virgin olive) will also do a good job.  Or cling film - depends what you're using as a mould.

One of the beauties of papier mâché is you don't need to go anywhere near an art shop or specialist supplies if you don't want to.  Experiment with your 'recipe' - you may not need to use whiting; I mostly use wallpaper paste (for the glue) and standard filler powder (Polyfilla, Tetrion for preference but I'm afraid I don't know the US equivalents) which has a fair amount of 'stick' built into it, with PVA for extra strength and a bit of flexibility.

I've used sawdust but more as a bulking agent in large-scale sculptures than for extra strength.

Hope that helps - keep experimenting, you'll find the method that suits you eventually!

Antonia

CatPerson wrote:

But you need special equipment for that, don't you?

Vacuum cleaner, ridged mold (plaster), and a big plastic bag.